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	$104.75	11.766%	$117.0749	$117.07	$117.05	$117.10
Purchase #2	$147.87	9.513%	$161.9369	$161.94	$161.95	$161.90
Purchase #3	$34.61	7.567%	$37.2289	$37.23	$37.25	$37.20
Purchase #4	$105.70	5.280%	$111.281	$111.28	$111.30	$111.30
Purchase #5	$125.68	13.690%	$142.8856	$142.89	$142.90	$142.90
Purchase #6	$149.63	13.243%	$169.4455	$169.45	$169.45	$169.40
Purchase #7	$58.33	10.416%	$64.4057	$64.41	$64.40	$64.40
7 purchase totals =	$726.57		$804.2585	$804.27	$804.30	$804.20