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 $96.87   9.408%   $105.9835   $105.98   $106.00   $106.00  
  Purchase #2 $168.28   10.351%   $185.6987   $185.70   $185.70   $185.70  
  Purchase #3 $100.71   9.582%   $110.36   $110.36   $110.35   $110.40  
  Purchase #4 $55.76   6.740%   $59.5182   $59.52   $59.50   $59.50  
  Purchase #5 $115.52   5.361%   $121.713   $121.71   $121.70   $121.70  
  Purchase #6 $187.88   5.390%   $198.0067   $198.01   $198.00   $198.00  
  Purchase #7 $216.27   12.507%   $243.3189   $243.32   $243.30   $243.30  
  7 purchase totals = $941.29       $1,024.5990   $1,024.60   $1,024.55   $1,024.60