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	$168.42	13.138%	$190.547	$190.55	$190.55	$190.50
Purchase #2	$226.57	10.851%	$251.1551	$251.16	$251.15	$251.20
Purchase #3	$177.97	7.576%	$191.453	$191.45	$191.45	$191.50
Purchase #4	$172.90	13.263%	$195.8317	$195.83	$195.85	$195.80
Purchase #5	$131.67	8.158%	$142.4116	$142.41	$142.40	$142.40
Purchase #6	$77.46	11.285%	$86.2014	$86.20	$86.20	$86.20
Purchase #7	$155.40	6.692%	$165.7994	$165.80	$165.80	$165.80
7 purchase totals =	$1,110.39		$1,223.3992	$1,223.40	$1,223.40	$1,223.40