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	$124.45	9.610%	$136.4096	$136.41	$136.40	$136.40
Purchase #2	$67.97	4.673%	$71.1462	$71.15	$71.15	$71.10
Purchase #3	$234.52	5.644%	$247.7563	$247.76	$247.75	$247.80
Purchase #4	$159.76	10.535%	$176.5907	$176.59	$176.60	$176.60
Purchase #5	$207.90	4.256%	$216.7482	$216.75	$216.75	$216.70
Purchase #6	$150.59	7.651%	$162.1116	$162.11	$162.10	$162.10
Purchase #7	$33.57	3.105%	$34.6123	$34.61	$34.60	$34.60
7 purchase totals =	$978.76		$1,045.3749	$1,045.38	$1,045.35	$1,045.30