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	$160.53	4.871%	$168.3494	$168.35	$168.35	$168.30
Purchase #2	$66.76	6.622%	$71.1808	$71.18	$71.20	$71.20
Purchase #3	$83.39	8.501%	$90.479	$90.48	$90.50	$90.50
Purchase #4	$83.66	4.837%	$87.7066	$87.71	$87.70	$87.70
Purchase #5	$154.77	4.332%	$161.4746	$161.47	$161.45	$161.50
Purchase #6	$89.34	9.757%	$98.0569	$98.06	$98.05	$98.10
Purchase #7	$222.89	13.231%	$252.3806	$252.38	$252.40	$252.40
7 purchase totals =	$861.34		$929.6279	$929.63	$929.65	$929.70