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	$167.26	3.579%	$173.2462	$173.25	$173.25	$173.20
Purchase #2	$77.25	8.645%	$83.9283	$83.93	$83.95	$83.90
Purchase #3	$13.63	11.403%	$15.1842	$15.18	$15.20	$15.20
Purchase #4	$59.97	4.461%	$62.6453	$62.65	$62.65	$62.60
Purchase #5	$98.94	7.487%	$106.3476	$106.35	$106.35	$106.30
Purchase #6	$55.51	10.299%	$61.227	$61.23	$61.25	$61.20
Purchase #7	$79.83	4.255%	$83.2268	$83.23	$83.25	$83.20
7 purchase totals =	$552.39		$585.8054	$585.82	$585.90	$585.60