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	$155.53	4.370%	$162.3267	$162.33	$162.35	$162.30
Purchase #2	$206.60	13.796%	$235.1025	$235.10	$235.10	$235.10
Purchase #3	$158.40	13.845%	$180.3305	$180.33	$180.35	$180.30
Purchase #4	$209.54	5.707%	$221.4984	$221.50	$221.50	$221.50
Purchase #5	$67.57	9.717%	$74.1358	$74.14	$74.15	$74.10
Purchase #6	$91.28	4.541%	$95.425	$95.43	$95.45	$95.40
Purchase #7	$94.67	6.567%	$100.887	$100.89	$100.90	$100.90
7 purchase totals =	$983.59		$1,069.7059	$1,069.72	$1,069.80	$1,069.60