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	$138.51	9.640%	$151.8624	$151.86	$151.85	$151.90
Purchase #2	$148.41	13.462%	$168.389	$168.39	$168.40	$168.40
Purchase #3	$159.68	4.171%	$166.3403	$166.34	$166.35	$166.30
Purchase #4	$229.93	7.471%	$247.1081	$247.11	$247.10	$247.10
Purchase #5	$42.55	7.279%	$45.6472	$45.65	$45.65	$45.60
Purchase #6	$228.95	9.438%	$250.5583	$250.56	$250.55	$250.60
Purchase #7	$46.71	12.394%	$52.4992	$52.50	$52.50	$52.50
7 purchase totals =	$994.74		$1,082.4045	$1,082.41	$1,082.40	$1,082.40