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	$221.88	11.516%	$247.4317	$247.43	$247.45	$247.40
Purchase #2	$65.37	5.199%	$68.7686	$68.77	$68.75	$68.80
Purchase #3	$215.51	3.344%	$222.7167	$222.72	$222.70	$222.70
Purchase #4	$154.50	11.547%	$172.3401	$172.34	$172.35	$172.30
Purchase #5	$237.61	7.166%	$254.6371	$254.64	$254.65	$254.60
Purchase #6	$173.95	3.114%	$179.3668	$179.37	$179.35	$179.40
Purchase #7	$42.72	8.470%	$46.3384	$46.34	$46.35	$46.30
7 purchase totals =	$1,111.54		$1,191.5994	$1,191.61	$1,191.60	$1,191.50