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	$114.86	9.625%	$125.9153	$125.92	$125.90	$125.90
Purchase #2	$73.91	13.321%	$83.7556	$83.76	$83.75	$83.80
Purchase #3	$15.51	13.487%	$17.6018	$17.60	$17.60	$17.60
Purchase #4	$13.78	9.603%	$15.1033	$15.10	$15.10	$15.10
Purchase #5	$28.84	12.356%	$32.4035	$32.40	$32.40	$32.40
Purchase #6	$60.61	3.871%	$62.9562	$62.96	$62.95	$63.00
Purchase #7	$85.29	6.400%	$90.7486	$90.75	$90.75	$90.70
7 purchase totals =	$392.80		$428.4843	$428.49	$428.45	$428.50