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 $60.52   8.548%   $65.6932   $65.69   $65.70   $65.70  
  Purchase #2 $44.58   9.240%   $48.6992   $48.70   $48.70   $48.70  
  Purchase #3 $174.58   4.228%   $181.9612   $181.96   $181.95   $182.00  
  Purchase #4 $200.28   11.747%   $223.8069   $223.81   $223.80   $223.80  
  Purchase #5 $157.47   8.477%   $170.8187   $170.82   $170.80   $170.80  
  Purchase #6 $193.54   7.388%   $207.8387   $207.84   $207.85   $207.80  
  Purchase #7 $240.68   7.516%   $258.7695   $258.77   $258.75   $258.80  
  7 purchase totals = $1,071.65       $1,157.5874   $1,157.59   $1,157.55   $1,157.60