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	$50.92	7.725%	$54.8536	$54.85	$54.85	$54.90
Purchase #2	$162.77	10.281%	$179.5044	$179.50	$179.50	$179.50
Purchase #3	$25.61	11.217%	$28.4827	$28.48	$28.50	$28.50
Purchase #4	$24.97	13.377%	$28.3102	$28.31	$28.30	$28.30
Purchase #5	$239.89	5.655%	$253.4558	$253.46	$253.45	$253.50
Purchase #6	$221.95	3.526%	$229.776	$229.78	$229.80	$229.80
Purchase #7	$121.65	10.766%	$134.7468	$134.75	$134.75	$134.70
7 purchase totals =	$847.76		$909.1295	$909.13	$909.15	$909.20