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 $60.77   12.816%   $68.5583   $68.56   $68.55   $68.60  
  Purchase #2 $112.31   12.768%   $126.6497   $126.65   $126.65   $126.60  
  Purchase #3 $210.70   11.722%   $235.3983   $235.40   $235.40   $235.40  
  Purchase #4 $63.65   7.172%   $68.215   $68.22   $68.20   $68.20  
  Purchase #5 $235.58   12.263%   $264.4692   $264.47   $264.45   $264.50  
  Purchase #6 $230.49   4.787%   $241.5236   $241.52   $241.50   $241.50  
  Purchase #7 $173.99   13.429%   $197.3551   $197.36   $197.35   $197.40  
  7 purchase totals = $1,087.49       $1,202.1692   $1,202.18   $1,202.10   $1,202.20