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 $176.82   11.426%   $197.0235   $197.02   $197.00   $197.00  
  Purchase #2 $173.51   10.500%   $191.7286   $191.73   $191.75   $191.70  
  Purchase #3 $84.89   8.153%   $91.8111   $91.81   $91.80   $91.80  
  Purchase #4 $202.83   10.110%   $223.3361   $223.34   $223.35   $223.30  
  Purchase #5 $88.86   12.477%   $99.9471   $99.95   $99.95   $99.90  
  Purchase #6 $134.57   8.334%   $145.7851   $145.79   $145.80   $145.80  
  Purchase #7 $134.65   8.309%   $145.8381   $145.84   $145.85   $145.80  
  7 purchase totals = $996.13       $1,095.4696   $1,095.48   $1,095.50   $1,095.30