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 $146.91   5.413%   $154.8622   $154.86   $154.85   $154.90  
  Purchase #2 $157.91   9.107%   $172.2909   $172.29   $172.30   $172.30  
  Purchase #3 $60.89   9.336%   $66.5747   $66.57   $66.55   $66.60  
  Purchase #4 $243.27   4.760%   $254.8497   $254.85   $254.85   $254.80  
  Purchase #5 $165.77   6.523%   $176.5832   $176.58   $176.60   $176.60  
  Purchase #6 $216.82   5.724%   $229.2308   $229.23   $229.25   $229.20  
  Purchase #7 $139.41   7.173%   $149.4099   $149.41   $149.40   $149.40  
  7 purchase totals = $1,130.98       $1,203.8014   $1,203.79   $1,203.80   $1,203.80