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	$246.83	9.209%	$269.5606	$269.56	$269.55	$269.60
Purchase #2	$101.86	10.342%	$112.3944	$112.39	$112.40	$112.40
Purchase #3	$128.70	13.498%	$146.0719	$146.07	$146.05	$146.10
Purchase #4	$131.89	13.469%	$149.6543	$149.65	$149.65	$149.70
Purchase #5	$246.31	3.816%	$255.7092	$255.71	$255.70	$255.70
Purchase #6	$13.94	12.502%	$15.6828	$15.68	$15.70	$15.70
Purchase #7	$185.36	5.456%	$195.4732	$195.47	$195.45	$195.50
7 purchase totals =	$1,054.89		$1,144.5464	$1,144.53	$1,144.50	$1,144.70