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	$222.95	7.400%	$239.4483	$239.45	$239.45	$239.40
Purchase #2	$42.35	8.482%	$45.9421	$45.94	$45.95	$45.90
Purchase #3	$28.98	3.397%	$29.9645	$29.96	$29.95	$30.00
Purchase #4	$219.82	11.514%	$245.1301	$245.13	$245.15	$245.10
Purchase #5	$103.82	7.388%	$111.4902	$111.49	$111.50	$111.50
Purchase #6	$144.76	4.472%	$151.2337	$151.23	$151.25	$151.20
Purchase #7	$206.38	10.572%	$228.1985	$228.20	$228.20	$228.20
7 purchase totals =	$969.06		$1,051.4074	$1,051.40	$1,051.45	$1,051.30