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	$87.43	3.632%	$90.6055	$90.61	$90.60	$90.60
Purchase #2	$89.74	4.273%	$93.5746	$93.57	$93.55	$93.60
Purchase #3	$239.87	3.714%	$248.7788	$248.78	$248.80	$248.80
Purchase #4	$150.73	13.554%	$171.1599	$171.16	$171.15	$171.20
Purchase #5	$161.33	5.225%	$169.7595	$169.76	$169.75	$169.80
Purchase #6	$55.52	8.466%	$60.2203	$60.22	$60.20	$60.20
Purchase #7	$49.95	4.610%	$52.2527	$52.25	$52.25	$52.30
7 purchase totals =	$834.57		$886.3513	$886.35	$886.30	$886.50