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	$34.51	11.690%	$38.5442	$38.54	$38.55	$38.50
Purchase #2	$168.57	12.851%	$190.2329	$190.23	$190.25	$190.20
Purchase #3	$28.69	11.238%	$31.9142	$31.91	$31.90	$31.90
Purchase #4	$130.88	3.699%	$135.7213	$135.72	$135.70	$135.70
Purchase #5	$221.60	10.795%	$245.5217	$245.52	$245.50	$245.50
Purchase #6	$17.48	6.577%	$18.6297	$18.63	$18.65	$18.60
Purchase #7	$243.90	12.815%	$275.1558	$275.16	$275.15	$275.20
7 purchase totals =	$845.63		$935.7198	$935.71	$935.70	$935.60