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	$184.73	3.150%	$190.549	$190.55	$190.55	$190.50
Purchase #2	$104.39	7.488%	$112.2067	$112.21	$112.20	$112.20
Purchase #3	$24.97	9.428%	$27.3242	$27.32	$27.30	$27.30
Purchase #4	$214.39	5.113%	$225.3518	$225.35	$225.35	$225.40
Purchase #5	$52.39	12.741%	$59.065	$59.07	$59.05	$59.10
Purchase #6	$225.28	7.627%	$242.4621	$242.46	$242.45	$242.50
Purchase #7	$95.53	12.866%	$107.8209	$107.82	$107.80	$107.80
7 purchase totals =	$901.68		$964.7797	$964.78	$964.70	$964.80