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	$169.89	6.604%	$181.1095	$181.11	$181.10	$181.10
Purchase #2	$36.73	7.575%	$39.5123	$39.51	$39.50	$39.50
Purchase #3	$75.96	9.678%	$83.3114	$83.31	$83.30	$83.30
Purchase #4	$150.75	9.433%	$164.9702	$164.97	$164.95	$165.00
Purchase #5	$59.93	3.106%	$61.7914	$61.79	$61.80	$61.80
Purchase #6	$69.51	12.723%	$78.3538	$78.35	$78.35	$78.40
Purchase #7	$91.64	8.422%	$99.3579	$99.36	$99.35	$99.40
7 purchase totals =	$654.41		$708.4065	$708.40	$708.35	$708.50