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	$152.90	13.393%	$173.3779	$173.38	$173.40	$173.40
Purchase #2	$151.34	3.234%	$156.2343	$156.23	$156.25	$156.20
Purchase #3	$160.36	7.705%	$172.7157	$172.72	$172.70	$172.70
Purchase #4	$247.89	3.241%	$255.9241	$255.92	$255.90	$255.90
Purchase #5	$246.54	3.560%	$255.3168	$255.32	$255.30	$255.30
Purchase #6	$238.28	9.575%	$261.0953	$261.10	$261.10	$261.10
Purchase #7	$164.65	10.533%	$181.9926	$181.99	$182.00	$182.00
7 purchase totals =	$1,361.96		$1,456.6567	$1,456.66	$1,456.65	$1,456.60