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	$100.57	10.819%	$111.4507	$111.45	$111.45	$111.50
Purchase #2	$41.41	10.209%	$45.6375	$45.64	$45.65	$45.60
Purchase #3	$37.78	7.278%	$40.5296	$40.53	$40.55	$40.50
Purchase #4	$31.54	7.262%	$33.8304	$33.83	$33.85	$33.80
Purchase #5	$26.95	13.269%	$30.526	$30.53	$30.55	$30.50
Purchase #6	$48.60	7.753%	$52.368	$52.37	$52.35	$52.40
Purchase #7	$152.68	11.261%	$169.8733	$169.87	$169.85	$169.90
7 purchase totals =	$439.53		$484.2155	$484.22	$484.25	$484.20