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 $114.85   10.262%   $126.6359   $126.64   $126.65   $126.60  
  Purchase #2 $188.65   6.856%   $201.5838   $201.58   $201.60   $201.60  
  Purchase #3 $245.61   8.791%   $267.2016   $267.20   $267.20   $267.20  
  Purchase #4 $29.91   13.254%   $33.8743   $33.87   $33.85   $33.90  
  Purchase #5 $43.50   12.847%   $49.0884   $49.09   $49.10   $49.10  
  Purchase #6 $203.84   7.797%   $219.7334   $219.73   $219.75   $219.70  
  Purchase #7 $147.41   3.125%   $152.0166   $152.02   $152.00   $152.00  
  7 purchase totals = $973.77       $1,050.1340   $1,050.13   $1,050.15   $1,050.10