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	$127.66	11.607%	$142.4775	$142.48	$142.50	$142.50
Purchase #2	$50.96	7.111%	$54.5838	$54.58	$54.60	$54.60
Purchase #3	$175.35	5.240%	$184.5383	$184.54	$184.55	$184.50
Purchase #4	$66.25	6.551%	$70.59	$70.59	$70.60	$70.60
Purchase #5	$84.30	13.589%	$95.7555	$95.76	$95.75	$95.80
Purchase #6	$118.91	5.492%	$125.4405	$125.44	$125.45	$125.40
Purchase #7	$76.43	3.761%	$79.3045	$79.30	$79.30	$79.30
7 purchase totals =	$699.86		$752.6901	$752.69	$752.75	$752.70