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 $87.29   11.810%   $97.5989   $97.60   $97.60   $97.60  
  Purchase #2 $241.47   9.170%   $263.6128   $263.61   $263.60   $263.60  
  Purchase #3 $190.75   3.748%   $197.8993   $197.90   $197.90   $197.90  
  Purchase #4 $171.80   6.850%   $183.5683   $183.57   $183.55   $183.60  
  Purchase #5 $179.74   4.524%   $187.8714   $187.87   $187.85   $187.90  
  Purchase #6 $219.85   10.816%   $243.629   $243.63   $243.65   $243.60  
  Purchase #7 $52.60   10.173%   $57.951   $57.95   $57.95   $58.00  
  7 purchase totals = $1,143.50       $1,232.1307   $1,232.13   $1,232.10   $1,232.20