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	$33.41	11.325%	$37.1937	$37.19	$37.20	$37.20
Purchase #2	$153.91	12.147%	$172.6054	$172.61	$172.60	$172.60
Purchase #3	$44.41	5.594%	$46.8943	$46.89	$46.90	$46.90
Purchase #4	$188.59	7.487%	$202.7097	$202.71	$202.70	$202.70
Purchase #5	$81.97	7.813%	$88.3743	$88.37	$88.35	$88.40
Purchase #6	$52.53	13.121%	$59.4225	$59.42	$59.40	$59.40
Purchase #7	$77.51	12.855%	$87.4739	$87.47	$87.45	$87.50
7 purchase totals =	$632.33		$694.6738	$694.66	$694.60	$694.70