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	$234.51	4.605%	$245.3092	$245.31	$245.30	$245.30
Purchase #2	$12.28	11.423%	$13.6827	$13.68	$13.70	$13.70
Purchase #3	$89.43	7.846%	$96.4467	$96.45	$96.45	$96.40
Purchase #4	$219.37	7.319%	$235.4257	$235.43	$235.45	$235.40
Purchase #5	$224.83	10.248%	$247.8706	$247.87	$247.85	$247.90
Purchase #6	$36.42	12.377%	$40.9277	$40.93	$40.95	$40.90
Purchase #7	$78.45	9.389%	$85.8157	$85.82	$85.80	$85.80
7 purchase totals =	$895.29		$965.4783	$965.49	$965.50	$965.40