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	$48.28	10.275%	$53.2408	$53.24	$53.25	$53.20
Purchase #2	$9.51	11.834%	$10.6354	$10.64	$10.65	$10.60
Purchase #3	$182.65	3.781%	$189.556	$189.56	$189.55	$189.60
Purchase #4	$22.86	12.169%	$25.6418	$25.64	$25.65	$25.60
Purchase #5	$74.68	10.421%	$82.4624	$82.46	$82.45	$82.50
Purchase #6	$152.46	3.275%	$157.4531	$157.45	$157.45	$157.50
Purchase #7	$153.54	8.722%	$166.9318	$166.93	$166.95	$166.90
7 purchase totals =	$643.98		$685.9213	$685.92	$685.95	$685.90