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	$145.86	7.245%	$156.4276	$156.43	$156.45	$156.40
Purchase #2	$80.83	3.696%	$83.8175	$83.82	$83.80	$83.80
Purchase #3	$145.85	11.422%	$162.509	$162.51	$162.50	$162.50
Purchase #4	$221.84	10.208%	$244.4854	$244.49	$244.50	$244.50
Purchase #5	$127.58	10.377%	$140.819	$140.82	$140.80	$140.80
Purchase #6	$94.31	4.748%	$98.7878	$98.79	$98.80	$98.80
Purchase #7	$199.72	8.409%	$216.5145	$216.51	$216.50	$216.50
7 purchase totals =	$1,015.99		$1,103.3608	$1,103.37	$1,103.35	$1,103.30