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	$10.91	5.561%	$11.5167	$11.52	$11.50	$11.50
Purchase #2	$22.53	6.827%	$24.0681	$24.07	$24.05	$24.10
Purchase #3	$67.66	6.322%	$71.9375	$71.94	$71.95	$71.90
Purchase #4	$28.57	13.663%	$32.4735	$32.47	$32.45	$32.50
Purchase #5	$79.65	4.277%	$83.0566	$83.06	$83.05	$83.10
Purchase #6	$32.78	3.199%	$33.8286	$33.83	$33.85	$33.80
Purchase #7	$239.71	10.766%	$265.5172	$265.52	$265.50	$265.50
7 purchase totals =	$481.81		$522.3982	$522.41	$522.35	$522.40