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	$209.82	10.636%	$232.1365	$232.14	$232.15	$232.10
Purchase #2	$133.88	8.749%	$145.5932	$145.59	$145.60	$145.60
Purchase #3	$64.34	12.389%	$72.3111	$72.31	$72.30	$72.30
Purchase #4	$35.65	5.523%	$37.6189	$37.62	$37.60	$37.60
Purchase #5	$74.74	7.530%	$80.3679	$80.37	$80.35	$80.40
Purchase #6	$225.76	8.367%	$244.6493	$244.65	$244.65	$244.60
Purchase #7	$48.53	9.829%	$53.3	$53.30	$53.30	$53.30
7 purchase totals =	$792.72		$865.9769	$865.98	$865.95	$865.90