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	$146.81	7.857%	$158.3449	$158.34	$158.35	$158.30
Purchase #2	$139.36	4.179%	$145.1839	$145.18	$145.20	$145.20
Purchase #3	$89.61	5.828%	$94.8325	$94.83	$94.85	$94.80
Purchase #4	$189.33	10.153%	$208.5527	$208.55	$208.55	$208.60
Purchase #5	$190.36	11.144%	$211.5737	$211.57	$211.55	$211.60
Purchase #6	$75.57	9.345%	$82.632	$82.63	$82.65	$82.60
Purchase #7	$46.52	8.145%	$50.3091	$50.31	$50.30	$50.30
7 purchase totals =	$877.56		$951.4288	$951.41	$951.45	$951.40