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	$149.68	10.523%	$165.4308	$165.43	$165.45	$165.40
Purchase #2	$20.78	3.730%	$21.5551	$21.56	$21.55	$21.60
Purchase #3	$239.87	6.846%	$256.2915	$256.29	$256.30	$256.30
Purchase #4	$223.56	9.561%	$244.9346	$244.93	$244.95	$244.90
Purchase #5	$158.75	3.465%	$164.2507	$164.25	$164.25	$164.30
Purchase #6	$128.62	8.816%	$139.9591	$139.96	$139.95	$140.00
Purchase #7	$123.56	9.549%	$135.3587	$135.36	$135.35	$135.40
7 purchase totals =	$1,044.82		$1,127.7805	$1,127.78	$1,127.80	$1,127.90