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 $62.55   11.457%   $69.7164   $69.72   $69.70   $69.70  
  Purchase #2 $217.85   9.545%   $238.6438   $238.64   $238.65   $238.60  
  Purchase #3 $165.57   4.131%   $172.4097   $172.41   $172.40   $172.40  
  Purchase #4 $48.93   4.458%   $51.1113   $51.11   $51.10   $51.10  
  Purchase #5 $193.29   5.862%   $204.6207   $204.62   $204.60   $204.60  
  Purchase #6 $230.84   6.837%   $246.6225   $246.62   $246.60   $246.60  
  Purchase #7 $72.31   11.869%   $80.8925   $80.89   $80.90   $80.90  
  7 purchase totals = $991.34       $1,064.0169   $1,064.01   $1,063.95   $1,063.90