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	$240.63	13.167%	$272.3138	$272.31	$272.30	$272.30
Purchase #2	$229.50	11.648%	$256.2322	$256.23	$256.25	$256.20
Purchase #3	$18.76	12.556%	$21.1155	$21.12	$21.10	$21.10
Purchase #4	$227.40	11.798%	$254.2287	$254.23	$254.25	$254.20
Purchase #5	$235.67	5.788%	$249.3106	$249.31	$249.30	$249.30
Purchase #6	$60.59	9.640%	$66.4309	$66.43	$66.45	$66.40
Purchase #7	$111.82	3.721%	$115.9808	$115.98	$116.00	$116.00
7 purchase totals =	$1,124.37		$1,235.6125	$1,235.61	$1,235.65	$1,235.50