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	$57.35	3.187%	$59.1777	$59.18	$59.20	$59.20
Purchase #2	$237.41	4.280%	$247.5711	$247.57	$247.55	$247.60
Purchase #3	$58.93	13.230%	$66.7264	$66.73	$66.75	$66.70
Purchase #4	$145.35	5.797%	$153.7759	$153.78	$153.80	$153.80
Purchase #5	$163.46	5.512%	$172.4699	$172.47	$172.45	$172.50
Purchase #6	$86.86	6.181%	$92.2288	$92.23	$92.25	$92.20
Purchase #7	$92.30	12.765%	$104.0821	$104.08	$104.10	$104.10
7 purchase totals =	$841.66		$896.0319	$896.04	$896.10	$896.10