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 $87.32   5.495%   $92.1182   $92.12   $92.10   $92.10  
  Purchase #2 $204.92   6.103%   $217.4263   $217.43   $217.45   $217.40  
  Purchase #3 $194.35   8.544%   $210.9553   $210.96   $210.95   $211.00  
  Purchase #4 $196.89   11.683%   $219.8927   $219.89   $219.90   $219.90  
  Purchase #5 $55.36   3.701%   $57.4089   $57.41   $57.40   $57.40  
  Purchase #6 $170.25   8.178%   $184.173   $184.17   $184.15   $184.20  
  Purchase #7 $219.31   8.170%   $237.2276   $237.23   $237.25   $237.20  
  7 purchase totals = $1,128.40       $1,219.2020   $1,219.21   $1,219.20   $1,219.20