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 $158.72   9.627%   $174   $174.00   $174.00   $174.00  
  Purchase #2 $44.80   8.344%   $48.5381   $48.54   $48.55   $48.50  
  Purchase #3 $211.42   6.857%   $225.9171   $225.92   $225.90   $225.90  
  Purchase #4 $231.70   11.206%   $257.6643   $257.66   $257.65   $257.70  
  Purchase #5 $123.94   8.364%   $134.3063   $134.31   $134.30   $134.30  
  Purchase #6 $86.71   5.835%   $91.7695   $91.77   $91.75   $91.80  
  Purchase #7 $106.45   6.141%   $112.9871   $112.99   $113.00   $113.00  
  7 purchase totals = $963.74       $1,045.1824   $1,045.19   $1,045.15   $1,045.20