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	$129.94	13.347%	$147.2831	$147.28	$147.30	$147.30
Purchase #2	$62.37	13.872%	$71.022	$71.02	$71.00	$71.00
Purchase #3	$87.99	3.437%	$91.0142	$91.01	$91.00	$91.00
Purchase #4	$175.51	10.659%	$194.2176	$194.22	$194.20	$194.20
Purchase #5	$37.45	13.382%	$42.4616	$42.46	$42.45	$42.50
Purchase #6	$159.66	3.702%	$165.5706	$165.57	$165.55	$165.60
Purchase #7	$15.42	13.328%	$17.4752	$17.48	$17.50	$17.50
7 purchase totals =	$668.34		$729.0443	$729.04	$729.00	$729.10