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	$234.56	3.444%	$242.6382	$242.64	$242.65	$242.60
Purchase #2	$30.94	5.154%	$32.5346	$32.53	$32.55	$32.50
Purchase #3	$101.39	5.199%	$106.6613	$106.66	$106.65	$106.70
Purchase #4	$48.62	4.391%	$50.7549	$50.75	$50.75	$50.80
Purchase #5	$191.68	12.111%	$214.8944	$214.89	$214.90	$214.90
Purchase #6	$158.91	13.558%	$180.455	$180.46	$180.45	$180.50
Purchase #7	$183.47	7.123%	$196.5386	$196.54	$196.55	$196.50
7 purchase totals =	$949.57		$1,024.4770	$1,024.47	$1,024.50	$1,024.50