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	$51.82	3.128%	$53.4409	$53.44	$53.45	$53.40
Purchase #2	$136.76	10.712%	$151.4097	$151.41	$151.40	$151.40
Purchase #3	$74.80	5.188%	$78.6806	$78.68	$78.70	$78.70
Purchase #4	$168.30	11.208%	$187.1631	$187.16	$187.15	$187.20
Purchase #5	$123.55	4.733%	$129.3976	$129.40	$129.40	$129.40
Purchase #6	$53.41	3.133%	$55.0833	$55.08	$55.10	$55.10
Purchase #7	$221.25	5.741%	$233.952	$233.95	$233.95	$234.00
7 purchase totals =	$829.89		$889.1272	$889.12	$889.15	$889.20