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	$148.36	12.791%	$167.3367	$167.34	$167.35	$167.30
Purchase #2	$179.68	3.429%	$185.8412	$185.84	$185.85	$185.80
Purchase #3	$43.53	5.148%	$45.7709	$45.77	$45.75	$45.80
Purchase #4	$137.86	11.325%	$153.4726	$153.47	$153.45	$153.50
Purchase #5	$219.49	12.760%	$247.4969	$247.50	$247.50	$247.50
Purchase #6	$137.80	12.397%	$154.8831	$154.88	$154.90	$154.90
Purchase #7	$84.73	4.673%	$88.6894	$88.69	$88.70	$88.70
7 purchase totals =	$951.45		$1,043.4908	$1,043.49	$1,043.50	$1,043.50