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	$214.47	12.540%	$241.3645	$241.36	$241.35	$241.40
Purchase #2	$64.62	11.816%	$72.2555	$72.26	$72.25	$72.30
Purchase #3	$237.41	10.305%	$261.8751	$261.88	$261.90	$261.90
Purchase #4	$161.72	7.496%	$173.8425	$173.84	$173.85	$173.80
Purchase #5	$195.38	9.635%	$214.2049	$214.20	$214.20	$214.20
Purchase #6	$188.45	4.459%	$196.853	$196.85	$196.85	$196.90
Purchase #7	$140.31	10.763%	$155.4116	$155.41	$155.40	$155.40
7 purchase totals =	$1,202.36		$1,315.8071	$1,315.80	$1,315.80	$1,315.90