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 $71.46   5.743%   $75.5639   $75.56   $75.55   $75.60  
  Purchase #2 $97.48   13.842%   $110.9732   $110.97   $110.95   $111.00  
  Purchase #3 $108.51   8.800%   $118.0589   $118.06   $118.05   $118.10  
  Purchase #4 $198.46   3.303%   $205.0151   $205.02   $205.00   $205.00  
  Purchase #5 $243.75   3.801%   $253.0149   $253.01   $253.00   $253.00  
  Purchase #6 $174.60   12.479%   $196.3883   $196.39   $196.40   $196.40  
  Purchase #7 $165.41   7.326%   $177.5279   $177.53   $177.55   $177.50  
  7 purchase totals = $1,059.67       $1,136.5422   $1,136.54   $1,136.50   $1,136.60