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	$198.34	11.251%	$220.6552	$220.66	$220.65	$220.70
Purchase #2	$139.72	7.192%	$149.7687	$149.77	$149.75	$149.80
Purchase #3	$49.46	12.221%	$55.5045	$55.50	$55.50	$55.50
Purchase #4	$159.72	7.850%	$172.258	$172.26	$172.25	$172.30
Purchase #5	$143.61	5.181%	$151.0504	$151.05	$151.05	$151.10
Purchase #6	$123.38	6.716%	$131.6662	$131.67	$131.65	$131.70
Purchase #7	$191.73	3.602%	$198.6361	$198.64	$198.65	$198.60
7 purchase totals =	$1,005.96		$1,079.5391	$1,079.55	$1,079.50	$1,079.70