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 $183.40   5.782%   $194.0042   $194.00   $194.00   $194.00  
  Purchase #2 $178.91   6.514%   $190.5642   $190.56   $190.55   $190.60  
  Purchase #3 $190.92   4.210%   $198.9577   $198.96   $198.95   $199.00  
  Purchase #4 $232.79   10.735%   $257.78   $257.78   $257.80   $257.80  
  Purchase #5 $144.41   8.121%   $156.1375   $156.14   $156.15   $156.10  
  Purchase #6 $31.64   8.823%   $34.4316   $34.43   $34.45   $34.40  
  Purchase #7 $24.41   9.694%   $26.7763   $26.78   $26.80   $26.80  
  7 purchase totals = $986.48       $1,058.6515   $1,058.65   $1,058.70   $1,058.70