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	$58.74	4.231%	$61.2253	$61.23	$61.25	$61.20
Purchase #2	$210.54	13.418%	$238.7903	$238.79	$238.80	$238.80
Purchase #3	$226.84	4.862%	$237.869	$237.87	$237.85	$237.90
Purchase #4	$40.52	7.689%	$43.6356	$43.64	$43.65	$43.60
Purchase #5	$223.48	11.788%	$249.8238	$249.82	$249.80	$249.80
Purchase #6	$24.72	13.693%	$28.1049	$28.10	$28.10	$28.10
Purchase #7	$92.49	8.292%	$100.1593	$100.16	$100.15	$100.20
7 purchase totals =	$877.33		$959.6082	$959.61	$959.60	$959.60