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	$128.48	10.144%	$141.513	$141.51	$141.50	$141.50
Purchase #2	$71.77	13.480%	$81.4446	$81.44	$81.45	$81.40
Purchase #3	$89.87	11.791%	$100.4666	$100.47	$100.45	$100.50
Purchase #4	$167.74	6.394%	$178.4653	$178.47	$178.45	$178.50
Purchase #5	$122.63	10.539%	$135.554	$135.55	$135.55	$135.60
Purchase #6	$134.39	13.271%	$152.2249	$152.22	$152.20	$152.20
Purchase #7	$111.48	10.356%	$123.0249	$123.02	$123.00	$123.00
7 purchase totals =	$826.36		$912.6933	$912.68	$912.60	$912.70