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 $190.82   7.156%   $204.4751   $204.48   $204.50   $204.50  
  Purchase #2 $98.60   5.538%   $104.0605   $104.06   $104.05   $104.10  
  Purchase #3 $69.96   5.728%   $73.9673   $73.97   $73.95   $74.00  
  Purchase #4 $203.89   7.706%   $219.6018   $219.60   $219.60   $219.60  
  Purchase #5 $231.68   6.365%   $246.4264   $246.43   $246.45   $246.40  
  Purchase #6 $152.72   4.493%   $159.5817   $159.58   $159.60   $159.60  
  Purchase #7 $6.29   7.694%   $6.774   $6.77   $6.75   $6.80  
  7 purchase totals = $953.96       $1,014.8868   $1,014.89   $1,014.90   $1,015.00