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	$22.42	7.708%	$24.1481	$24.15	$24.15	$24.10
Purchase #2	$30.25	10.538%	$33.4377	$33.44	$33.45	$33.40
Purchase #3	$44.97	4.326%	$46.9154	$46.92	$46.90	$46.90
Purchase #4	$204.45	8.657%	$222.1492	$222.15	$222.15	$222.10
Purchase #5	$76.25	3.140%	$78.6443	$78.64	$78.65	$78.60
Purchase #6	$156.55	10.852%	$173.5388	$173.54	$173.55	$173.50
Purchase #7	$142.87	8.437%	$154.9239	$154.92	$154.90	$154.90
7 purchase totals =	$677.76		$733.7574	$733.76	$733.75	$733.50