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	$181.64	8.301%	$196.7179	$196.72	$196.70	$196.70
Purchase #2	$90.96	11.246%	$101.1894	$101.19	$101.20	$101.20
Purchase #3	$65.43	7.661%	$70.4426	$70.44	$70.45	$70.40
Purchase #4	$47.82	5.644%	$50.519	$50.52	$50.50	$50.50
Purchase #5	$246.54	3.376%	$254.8632	$254.86	$254.85	$254.90
Purchase #6	$72.90	8.390%	$79.0163	$79.02	$79.00	$79.00
Purchase #7	$10.25	13.180%	$11.601	$11.60	$11.60	$11.60
7 purchase totals =	$715.54		$764.3494	$764.35	$764.30	$764.30