Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $191.49   9.544%   $209.7658   $209.77   $209.75   $209.80  
  Purchase #2 $96.98   7.798%   $104.5425   $104.54   $104.55   $104.50  
  Purchase #3 $109.37   10.481%   $120.8331   $120.83   $120.85   $120.80  
  Purchase #4 $136.32   6.581%   $145.2912   $145.29   $145.30   $145.30  
  Purchase #5 $107.92   5.371%   $113.7164   $113.72   $113.70   $113.70  
  Purchase #6 $210.82   3.386%   $217.9584   $217.96   $217.95   $218.00  
  Purchase #7 $178.70   12.519%   $201.0715   $201.07   $201.05   $201.10  
  7 purchase totals = $1,031.60       $1,113.1789   $1,113.18   $1,113.15   $1,113.20