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	$57.94	13.660%	$65.8546	$65.85	$65.85	$65.90
Purchase #2	$121.80	6.839%	$130.1299	$130.13	$130.15	$130.10
Purchase #3	$80.73	11.298%	$89.8509	$89.85	$89.85	$89.90
Purchase #4	$14.90	12.381%	$16.7448	$16.74	$16.75	$16.70
Purchase #5	$49.28	12.186%	$55.2853	$55.29	$55.30	$55.30
Purchase #6	$11.68	10.395%	$12.8941	$12.89	$12.90	$12.90
Purchase #7	$84.92	12.864%	$95.8441	$95.84	$95.85	$95.80
7 purchase totals =	$421.25		$466.6037	$466.59	$466.65	$466.60