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	$137.87	11.203%	$153.3156	$153.32	$153.30	$153.30
Purchase #2	$126.59	4.166%	$131.8637	$131.86	$131.85	$131.90
Purchase #3	$100.27	13.606%	$113.9127	$113.91	$113.90	$113.90
Purchase #4	$109.89	10.218%	$121.1186	$121.12	$121.10	$121.10
Purchase #5	$199.89	4.545%	$208.975	$208.98	$209.00	$209.00
Purchase #6	$250.70	8.721%	$272.5635	$272.56	$272.55	$272.60
Purchase #7	$72.31	11.680%	$80.7558	$80.76	$80.75	$80.80
7 purchase totals =	$997.52		$1,082.5049	$1,082.51	$1,082.45	$1,082.60