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	$55.85	10.160%	$61.5244	$61.52	$61.50	$61.50
Purchase #2	$96.33	9.445%	$105.4284	$105.43	$105.45	$105.40
Purchase #3	$179.81	13.196%	$203.5377	$203.54	$203.55	$203.50
Purchase #4	$140.49	11.328%	$156.4047	$156.40	$156.40	$156.40
Purchase #5	$27.74	9.326%	$30.327	$30.33	$30.35	$30.30
Purchase #6	$105.99	5.271%	$111.5767	$111.58	$111.60	$111.60
Purchase #7	$144.57	9.215%	$157.8921	$157.89	$157.90	$157.90
7 purchase totals =	$750.78		$826.6910	$826.69	$826.75	$826.60