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	$145.69	4.627%	$152.4311	$152.43	$152.45	$152.40
Purchase #2	$148.85	7.809%	$160.4737	$160.47	$160.45	$160.50
Purchase #3	$227.75	11.590%	$254.1462	$254.15	$254.15	$254.10
Purchase #4	$53.71	13.225%	$60.8131	$60.81	$60.80	$60.80
Purchase #5	$137.33	11.159%	$152.6547	$152.65	$152.65	$152.70
Purchase #6	$20.33	7.798%	$21.9153	$21.92	$21.90	$21.90
Purchase #7	$141.73	9.254%	$154.8457	$154.85	$154.85	$154.80
7 purchase totals =	$875.39		$957.2798	$957.28	$957.25	$957.20