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 $62.55   12.833%   $70.577   $70.58   $70.60   $70.60  
  Purchase #2 $194.52   8.142%   $210.3578   $210.36   $210.35   $210.40  
  Purchase #3 $202.67   4.870%   $212.54   $212.54   $212.55   $212.50  
  Purchase #4 $109.28   8.499%   $118.5677   $118.57   $118.55   $118.60  
  Purchase #5 $97.37   9.354%   $106.478   $106.48   $106.50   $106.50  
  Purchase #6 $196.58   11.757%   $219.6919   $219.69   $219.70   $219.70  
  Purchase #7 $238.25   7.245%   $255.5112   $255.51   $255.50   $255.50  
  7 purchase totals = $1,101.22       $1,193.7236   $1,193.73   $1,193.75   $1,193.80