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	$241.55	4.757%	$253.0405	$253.04	$253.05	$253.00
Purchase #2	$132.29	5.172%	$139.132	$139.13	$139.15	$139.10
Purchase #3	$68.30	9.607%	$74.8616	$74.86	$74.85	$74.90
Purchase #4	$103.69	7.368%	$111.3299	$111.33	$111.35	$111.30
Purchase #5	$207.95	10.249%	$229.2628	$229.26	$229.25	$229.30
Purchase #6	$56.89	13.562%	$64.6054	$64.61	$64.60	$64.60
Purchase #7	$169.61	13.340%	$192.236	$192.24	$192.25	$192.20
7 purchase totals =	$980.28		$1,064.4682	$1,064.47	$1,064.50	$1,064.40