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	$107.45	8.282%	$116.349	$116.35	$116.35	$116.30
Purchase #2	$61.37	10.680%	$67.9243	$67.92	$67.90	$67.90
Purchase #3	$228.61	8.463%	$247.9573	$247.96	$247.95	$248.00
Purchase #4	$188.48	11.491%	$210.1382	$210.14	$210.15	$210.10
Purchase #5	$65.45	7.782%	$70.5433	$70.54	$70.55	$70.50
Purchase #6	$91.84	4.397%	$95.8782	$95.88	$95.90	$95.90
Purchase #7	$63.86	5.694%	$67.4962	$67.50	$67.50	$67.50
7 purchase totals =	$807.06		$876.2865	$876.29	$876.30	$876.20