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	$36.47	6.253%	$38.7505	$38.75	$38.75	$38.80
Purchase #2	$85.61	4.732%	$89.6611	$89.66	$89.65	$89.70
Purchase #3	$94.58	12.243%	$106.1594	$106.16	$106.15	$106.20
Purchase #4	$98.58	7.161%	$105.6393	$105.64	$105.65	$105.60
Purchase #5	$57.45	11.659%	$64.1481	$64.15	$64.15	$64.10
Purchase #6	$126.77	13.634%	$144.0538	$144.05	$144.05	$144.10
Purchase #7	$21.51	5.112%	$22.6096	$22.61	$22.60	$22.60
7 purchase totals =	$520.97		$571.0218	$571.02	$571.00	$571.10