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	$204.57	6.649%	$218.1719	$218.17	$218.15	$218.20
Purchase #2	$233.93	3.819%	$242.8638	$242.86	$242.85	$242.90
Purchase #3	$167.49	5.349%	$176.449	$176.45	$176.45	$176.40
Purchase #4	$193.52	7.816%	$208.6455	$208.65	$208.65	$208.60
Purchase #5	$35.41	6.208%	$37.6083	$37.61	$37.60	$37.60
Purchase #6	$233.34	9.386%	$255.2413	$255.24	$255.25	$255.20
Purchase #7	$174.37	11.622%	$194.6353	$194.64	$194.65	$194.60
7 purchase totals =	$1,242.63		$1,333.6151	$1,333.62	$1,333.60	$1,333.50