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 $174.42   12.415%   $196.0742   $196.07   $196.05   $196.10  
  Purchase #2 $236.50   4.192%   $246.4141   $246.41   $246.40   $246.40  
  Purchase #3 $209.26   6.827%   $223.5462   $223.55   $223.55   $223.50  
  Purchase #4 $6.47   5.732%   $6.8409   $6.84   $6.85   $6.80  
  Purchase #5 $217.41   11.779%   $243.0187   $243.02   $243.00   $243.00  
  Purchase #6 $156.82   3.819%   $162.809   $162.81   $162.80   $162.80  
  Purchase #7 $60.90   3.744%   $63.1801   $63.18   $63.20   $63.20  
  7 purchase totals = $1,061.78       $1,141.8832   $1,141.88   $1,141.85   $1,141.80