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 $70.81   5.842%   $74.9467   $74.95   $74.95   $74.90  
  Purchase #2 $33.82   7.422%   $36.3301   $36.33   $36.35   $36.30  
  Purchase #3 $34.69   12.609%   $39.0641   $39.06   $39.05   $39.10  
  Purchase #4 $118.55   12.821%   $133.7493   $133.75   $133.75   $133.70  
  Purchase #5 $165.74   6.448%   $176.4269   $176.43   $176.45   $176.40  
  Purchase #6 $150.85   11.187%   $167.7256   $167.73   $167.75   $167.70  
  Purchase #7 $101.81   5.155%   $107.0583   $107.06   $107.05   $107.10  
  7 purchase totals = $676.27       $735.3010   $735.31   $735.35   $735.20