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	$52.39	10.601%	$57.9439	$57.94	$57.95	$57.90
Purchase #2	$242.61	5.716%	$256.4776	$256.48	$256.50	$256.50
Purchase #3	$68.60	13.866%	$78.1121	$78.11	$78.10	$78.10
Purchase #4	$49.38	11.564%	$55.0903	$55.09	$55.10	$55.10
Purchase #5	$137.44	5.215%	$144.6075	$144.61	$144.60	$144.60
Purchase #6	$26.86	6.729%	$28.6674	$28.67	$28.65	$28.70
Purchase #7	$146.60	10.113%	$161.4257	$161.43	$161.45	$161.40
7 purchase totals =	$723.88		$782.3245	$782.33	$782.35	$782.30