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	$62.25	3.820%	$64.628	$64.63	$64.65	$64.60
Purchase #2	$89.93	11.530%	$100.2989	$100.30	$100.30	$100.30
Purchase #3	$35.65	5.442%	$37.5901	$37.59	$37.60	$37.60
Purchase #4	$113.76	11.828%	$127.2155	$127.22	$127.20	$127.20
Purchase #5	$50.60	9.294%	$55.3028	$55.30	$55.30	$55.30
Purchase #6	$95.65	5.798%	$101.1958	$101.20	$101.20	$101.20
Purchase #7	$135.77	10.749%	$150.3639	$150.36	$150.35	$150.40
7 purchase totals =	$583.61		$636.5950	$636.60	$636.60	$636.60