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	$67.98	6.851%	$72.6373	$72.64	$72.65	$72.60
Purchase #2	$140.53	10.443%	$155.2055	$155.21	$155.20	$155.20
Purchase #3	$41.46	7.684%	$44.6458	$44.65	$44.65	$44.60
Purchase #4	$91.48	7.194%	$98.0611	$98.06	$98.05	$98.10
Purchase #5	$137.38	5.125%	$144.4207	$144.42	$144.40	$144.40
Purchase #6	$162.89	13.270%	$184.5055	$184.51	$184.50	$184.50
Purchase #7	$20.43	6.394%	$21.7363	$21.74	$21.75	$21.70
7 purchase totals =	$662.15		$721.2122	$721.23	$721.20	$721.10