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	$207.59	11.174%	$230.7861	$230.79	$230.80	$230.80
Purchase #2	$13.54	13.532%	$15.3722	$15.37	$15.35	$15.40
Purchase #3	$130.54	12.134%	$146.3797	$146.38	$146.40	$146.40
Purchase #4	$35.95	9.643%	$39.4167	$39.42	$39.40	$39.40
Purchase #5	$189.81	3.181%	$195.8479	$195.85	$195.85	$195.80
Purchase #6	$32.61	3.605%	$33.7856	$33.79	$33.80	$33.80
Purchase #7	$66.48	8.745%	$72.2937	$72.29	$72.30	$72.30
7 purchase totals =	$676.52		$733.8819	$733.89	$733.90	$733.90