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	$234.63	13.324%	$265.8921	$265.89	$265.90	$265.90
Purchase #2	$189.79	10.387%	$209.5035	$209.50	$209.50	$209.50
Purchase #3	$152.52	4.303%	$159.0829	$159.08	$159.10	$159.10
Purchase #4	$226.82	7.430%	$243.6727	$243.67	$243.65	$243.70
Purchase #5	$155.85	13.811%	$177.3744	$177.37	$177.35	$177.40
Purchase #6	$73.34	13.813%	$83.4705	$83.47	$83.45	$83.50
Purchase #7	$50.98	13.259%	$57.7394	$57.74	$57.75	$57.70
7 purchase totals =	$1,083.93		$1,196.7355	$1,196.72	$1,196.70	$1,196.80