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	$56.36	5.307%	$59.351	$59.35	$59.35	$59.40
Purchase #2	$187.82	12.459%	$211.2205	$211.22	$211.20	$211.20
Purchase #3	$106.92	10.179%	$117.8034	$117.80	$117.80	$117.80
Purchase #4	$231.34	9.170%	$252.5539	$252.55	$252.55	$252.60
Purchase #5	$99.56	12.175%	$111.6814	$111.68	$111.70	$111.70
Purchase #6	$232.39	10.242%	$256.1914	$256.19	$256.20	$256.20
Purchase #7	$78.78	12.618%	$88.7205	$88.72	$88.70	$88.70
7 purchase totals =	$993.17		$1,097.5221	$1,097.51	$1,097.50	$1,097.60