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	$18.30	5.324%	$19.2743	$19.27	$19.25	$19.30
Purchase #2	$199.78	11.204%	$222.1634	$222.16	$222.15	$222.20
Purchase #3	$124.63	5.503%	$131.4884	$131.49	$131.50	$131.50
Purchase #4	$42.92	10.200%	$47.2978	$47.30	$47.30	$47.30
Purchase #5	$120.61	11.228%	$134.1521	$134.15	$134.15	$134.20
Purchase #6	$131.55	4.769%	$137.8236	$137.82	$137.80	$137.80
Purchase #7	$240.97	11.724%	$269.2213	$269.22	$269.20	$269.20
7 purchase totals =	$878.76		$961.4209	$961.41	$961.35	$961.50