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	$191.38	7.280%	$205.3125	$205.31	$205.30	$205.30
Purchase #2	$42.34	8.762%	$46.0498	$46.05	$46.05	$46.00
Purchase #3	$74.76	12.158%	$83.8493	$83.85	$83.85	$83.80
Purchase #4	$26.35	6.422%	$28.0422	$28.04	$28.05	$28.00
Purchase #5	$39.78	13.389%	$45.1061	$45.11	$45.10	$45.10
Purchase #6	$64.74	9.190%	$70.6896	$70.69	$70.70	$70.70
Purchase #7	$50.93	10.637%	$56.3474	$56.35	$56.35	$56.30
7 purchase totals =	$490.28		$535.3969	$535.40	$535.40	$535.20