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	$218.47	11.737%	$244.1118	$244.11	$244.10	$244.10
Purchase #2	$17.51	9.391%	$19.1544	$19.15	$19.15	$19.20
Purchase #3	$137.32	4.635%	$143.6848	$143.68	$143.70	$143.70
Purchase #4	$105.54	6.449%	$112.3463	$112.35	$112.35	$112.30
Purchase #5	$60.69	10.873%	$67.2888	$67.29	$67.30	$67.30
Purchase #6	$165.63	7.850%	$178.632	$178.63	$178.65	$178.60
Purchase #7	$38.53	9.174%	$42.0647	$42.06	$42.05	$42.10
7 purchase totals =	$743.69		$807.2828	$807.27	$807.30	$807.30