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 $181.53   13.314%   $205.6989   $205.70   $205.70   $205.70  
  Purchase #2 $209.77   4.700%   $219.6292   $219.63   $219.65   $219.60  
  Purchase #3 $60.67   4.488%   $63.3929   $63.39   $63.40   $63.40  
  Purchase #4 $36.82   13.401%   $41.7542   $41.75   $41.75   $41.80  
  Purchase #5 $203.95   7.755%   $219.7663   $219.77   $219.75   $219.80  
  Purchase #6 $181.87   12.607%   $204.7984   $204.80   $204.80   $204.80  
  Purchase #7 $181.95   12.265%   $204.2662   $204.27   $204.25   $204.30  
  7 purchase totals = $1,056.56       $1,159.3061   $1,159.31   $1,159.30   $1,159.40