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 $211.25   5.532%   $222.9364   $222.94   $222.95   $222.90  
  Purchase #2 $172.44   11.718%   $192.6465   $192.65   $192.65   $192.60  
  Purchase #3 $212.29   5.134%   $223.189   $223.19   $223.20   $223.20  
  Purchase #4 $224.25   4.271%   $233.8277   $233.83   $233.85   $233.80  
  Purchase #5 $149.26   8.439%   $161.8561   $161.86   $161.85   $161.90  
  Purchase #6 $200.74   5.265%   $211.309   $211.31   $211.30   $211.30  
  Purchase #7 $16.29   13.147%   $18.4316   $18.43   $18.45   $18.40  
  7 purchase totals = $1,186.52       $1,264.1963   $1,264.21   $1,264.25   $1,264.10