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	$195.97	3.734%	$203.2875	$203.29	$203.30	$203.30
Purchase #2	$170.76	13.327%	$193.5172	$193.52	$193.50	$193.50
Purchase #3	$159.91	7.714%	$172.2455	$172.25	$172.25	$172.20
Purchase #4	$53.42	10.723%	$59.1482	$59.15	$59.15	$59.10
Purchase #5	$77.88	10.524%	$86.0761	$86.08	$86.10	$86.10
Purchase #6	$228.89	8.269%	$247.8169	$247.82	$247.80	$247.80
Purchase #7	$37.86	4.442%	$39.5417	$39.54	$39.55	$39.50
7 purchase totals =	$924.69		$1,001.6331	$1,001.65	$1,001.65	$1,001.50