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	$125.48	7.108%	$134.3991	$134.40	$134.40	$134.40
Purchase #2	$72.37	13.409%	$82.0741	$82.07	$82.05	$82.10
Purchase #3	$53.83	10.178%	$59.3088	$59.31	$59.30	$59.30
Purchase #4	$147.93	9.352%	$161.7644	$161.76	$161.75	$161.80
Purchase #5	$140.37	7.289%	$150.6016	$150.60	$150.60	$150.60
Purchase #6	$87.28	6.350%	$92.8223	$92.82	$92.80	$92.80
Purchase #7	$41.94	11.211%	$46.6419	$46.64	$46.65	$46.60
7 purchase totals =	$669.20		$727.6122	$727.60	$727.55	$727.60