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 $67.39   9.746%   $73.9578   $73.96   $73.95   $74.00  
  Purchase #2 $117.54   4.353%   $122.6565   $122.66   $122.65   $122.70  
  Purchase #3 $247.68   7.868%   $267.1675   $267.17   $267.15   $267.20  
  Purchase #4 $18.34   7.799%   $19.7703   $19.77   $19.75   $19.80  
  Purchase #5 $148.99   8.456%   $161.5886   $161.59   $161.60   $161.60  
  Purchase #6 $249.34   13.712%   $283.5295   $283.53   $283.55   $283.50  
  Purchase #7 $162.98   11.510%   $181.739   $181.74   $181.75   $181.70  
  7 purchase totals = $1,012.26       $1,110.4092   $1,110.42   $1,110.40   $1,110.50