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	$140.51	4.789%	$147.239	$147.24	$147.25	$147.20
Purchase #2	$77.87	6.802%	$83.1667	$83.17	$83.15	$83.20
Purchase #3	$175.34	9.421%	$191.8588	$191.86	$191.85	$191.90
Purchase #4	$39.31	3.189%	$40.5636	$40.56	$40.55	$40.60
Purchase #5	$42.77	12.238%	$48.0042	$48.00	$48.00	$48.00
Purchase #6	$8.97	13.840%	$10.2114	$10.21	$10.20	$10.20
Purchase #7	$190.37	10.555%	$210.4636	$210.46	$210.45	$210.50
7 purchase totals =	$675.14		$731.5073	$731.50	$731.45	$731.60