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 $161.37   9.809%   $177.1988   $177.20   $177.20   $177.20  
  Purchase #2 $60.70   12.566%   $68.3276   $68.33   $68.35   $68.30  
  Purchase #3 $195.80   4.644%   $204.893   $204.89   $204.90   $204.90  
  Purchase #4 $185.54   3.110%   $191.3103   $191.31   $191.30   $191.30  
  Purchase #5 $18.41   11.564%   $20.5389   $20.54   $20.55   $20.50  
  Purchase #6 $227.37   11.362%   $253.2038   $253.20   $253.20   $253.20  
  Purchase #7 $163.94   9.660%   $179.7766   $179.78   $179.80   $179.80  
  7 purchase totals = $1,013.13       $1,095.2490   $1,095.25   $1,095.30   $1,095.20