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 $200.72   5.490%   $211.7395   $211.74   $211.75   $211.70  
  Purchase #2 $235.58   6.802%   $251.6042   $251.60   $251.60   $251.60  
  Purchase #3 $49.70   9.691%   $54.5164   $54.52   $54.50   $54.50  
  Purchase #4 $89.34   8.433%   $96.874   $96.87   $96.85   $96.90  
  Purchase #5 $62.95   5.722%   $66.552   $66.55   $66.55   $66.60  
  Purchase #6 $148.32   3.253%   $153.1448   $153.14   $153.15   $153.10  
  Purchase #7 $213.36   5.466%   $225.0223   $225.02   $225.00   $225.00  
  7 purchase totals = $999.97       $1,059.4532   $1,059.44   $1,059.40   $1,059.40