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	$99.45	4.740%	$104.1639	$104.16	$104.15	$104.20
Purchase #2	$85.46	4.345%	$89.1732	$89.17	$89.15	$89.20
Purchase #3	$249.58	13.823%	$284.0794	$284.08	$284.10	$284.10
Purchase #4	$233.74	4.327%	$243.8539	$243.85	$243.85	$243.90
Purchase #5	$9.94	7.294%	$10.665	$10.67	$10.65	$10.70
Purchase #6	$115.88	6.560%	$123.4817	$123.48	$123.50	$123.50
Purchase #7	$15.56	8.265%	$16.846	$16.85	$16.85	$16.80
7 purchase totals =	$809.61		$872.2631	$872.26	$872.25	$872.40