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 $187.29   7.294%   $200.9509   $200.95   $200.95   $201.00  
  Purchase #2 $74.52   3.264%   $76.9523   $76.95   $76.95   $77.00  
  Purchase #3 $165.32   11.604%   $184.5037   $184.50   $184.50   $184.50  
  Purchase #4 $178.37   8.239%   $193.0659   $193.07   $193.05   $193.10  
  Purchase #5 $181.50   12.284%   $203.7955   $203.80   $203.80   $203.80  
  Purchase #6 $211.44   7.544%   $227.391   $227.39   $227.40   $227.40  
  Purchase #7 $98.68   4.317%   $102.94   $102.94   $102.95   $102.90  
  7 purchase totals = $1,097.12       $1,189.5993   $1,189.60   $1,189.60   $1,189.70