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	$140.43	4.676%	$146.9965	$147.00	$147.00	$147.00
Purchase #2	$150.47	4.145%	$156.707	$156.71	$156.70	$156.70
Purchase #3	$103.59	7.543%	$111.4038	$111.40	$111.40	$111.40
Purchase #4	$210.98	3.650%	$218.6808	$218.68	$218.70	$218.70
Purchase #5	$116.75	12.206%	$131.0005	$131.00	$131.00	$131.00
Purchase #6	$57.30	12.282%	$64.3376	$64.34	$64.35	$64.30
Purchase #7	$117.49	8.460%	$127.4297	$127.43	$127.45	$127.40
7 purchase totals =	$897.01		$956.5559	$956.56	$956.60	$956.50