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	$185.66	12.117%	$208.1564	$208.16	$208.15	$208.20
Purchase #2	$199.61	10.283%	$220.1359	$220.14	$220.15	$220.10
Purchase #3	$86.68	7.204%	$92.9244	$92.92	$92.90	$92.90
Purchase #4	$36.49	5.155%	$38.3711	$38.37	$38.35	$38.40
Purchase #5	$81.28	10.533%	$89.8412	$89.84	$89.85	$89.80
Purchase #6	$54.89	12.180%	$61.5756	$61.58	$61.60	$61.60
Purchase #7	$35.37	13.226%	$40.048	$40.05	$40.05	$40.00
7 purchase totals =	$679.98		$751.0526	$751.06	$751.05	$751.00