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	$231.49	10.223%	$255.1552	$255.16	$255.15	$255.20
Purchase #2	$44.53	12.184%	$49.9555	$49.96	$49.95	$50.00
Purchase #3	$31.61	11.648%	$35.2919	$35.29	$35.30	$35.30
Purchase #4	$244.78	3.826%	$254.1453	$254.15	$254.15	$254.10
Purchase #5	$125.82	9.116%	$137.2898	$137.29	$137.30	$137.30
Purchase #6	$77.35	4.556%	$80.8741	$80.87	$80.85	$80.90
Purchase #7	$224.87	11.497%	$250.7233	$250.72	$250.70	$250.70
7 purchase totals =	$980.45		$1,063.4351	$1,063.44	$1,063.40	$1,063.50