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	$177.86	13.712%	$202.2482	$202.25	$202.25	$202.20
Purchase #2	$75.61	12.822%	$85.3047	$85.30	$85.30	$85.30
Purchase #3	$190.31	12.399%	$213.9065	$213.91	$213.90	$213.90
Purchase #4	$99.71	13.800%	$113.47	$113.47	$113.45	$113.50
Purchase #5	$72.45	7.696%	$78.0258	$78.03	$78.05	$78.00
Purchase #6	$7.29	12.413%	$8.1949	$8.19	$8.20	$8.20
Purchase #7	$65.32	10.843%	$72.4026	$72.40	$72.40	$72.40
7 purchase totals =	$688.55		$773.5527	$773.55	$773.55	$773.50