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	$209.79	11.241%	$233.3725	$233.37	$233.35	$233.40
Purchase #2	$84.77	5.355%	$89.3094	$89.31	$89.30	$89.30
Purchase #3	$122.85	13.709%	$139.6915	$139.69	$139.70	$139.70
Purchase #4	$62.57	12.814%	$70.5877	$70.59	$70.60	$70.60
Purchase #5	$243.57	5.452%	$256.8494	$256.85	$256.85	$256.80
Purchase #6	$175.25	11.575%	$195.5352	$195.54	$195.55	$195.50
Purchase #7	$216.62	9.674%	$237.5758	$237.58	$237.60	$237.60
7 purchase totals =	$1,115.42		$1,222.9215	$1,222.93	$1,222.95	$1,222.90