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	$37.48	13.729%	$42.6256	$42.63	$42.65	$42.60
Purchase #2	$100.68	4.380%	$105.0898	$105.09	$105.10	$105.10
Purchase #3	$43.41	11.200%	$48.2719	$48.27	$48.25	$48.30
Purchase #4	$59.42	12.203%	$66.671	$66.67	$66.65	$66.70
Purchase #5	$58.81	6.378%	$62.5609	$62.56	$62.55	$62.60
Purchase #6	$63.38	6.475%	$67.4839	$67.48	$67.50	$67.50
Purchase #7	$64.26	8.292%	$69.5884	$69.59	$69.60	$69.60
7 purchase totals =	$427.44		$462.2915	$462.29	$462.30	$462.40