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	$79.35	4.247%	$82.72	$82.72	$82.70	$82.70
Purchase #2	$225.76	13.526%	$256.2963	$256.30	$256.30	$256.30
Purchase #3	$151.36	9.347%	$165.5076	$165.51	$165.50	$165.50
Purchase #4	$19.38	6.457%	$20.6314	$20.63	$20.65	$20.60
Purchase #5	$101.41	8.268%	$109.7946	$109.79	$109.80	$109.80
Purchase #6	$209.78	5.857%	$222.0668	$222.07	$222.05	$222.10
Purchase #7	$26.53	6.281%	$28.1963	$28.20	$28.20	$28.20
7 purchase totals =	$813.57		$885.2130	$885.22	$885.20	$885.20