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	$191.88	11.786%	$214.495	$214.50	$214.50	$214.50
Purchase #2	$184.35	3.279%	$190.3948	$190.39	$190.40	$190.40
Purchase #3	$29.73	8.428%	$32.2356	$32.24	$32.25	$32.20
Purchase #4	$166.81	4.344%	$174.0562	$174.06	$174.05	$174.10
Purchase #5	$51.39	9.254%	$56.1456	$56.15	$56.15	$56.10
Purchase #6	$225.94	13.326%	$256.0488	$256.05	$256.05	$256.00
Purchase #7	$42.27	8.781%	$45.9817	$45.98	$46.00	$46.00
7 purchase totals =	$892.37		$969.3577	$969.37	$969.40	$969.30