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	$142.38	3.644%	$147.5683	$147.57	$147.55	$147.60
Purchase #2	$78.35	5.698%	$82.8144	$82.81	$82.80	$82.80
Purchase #3	$178.62	5.190%	$187.8904	$187.89	$187.90	$187.90
Purchase #4	$246.88	3.169%	$254.7036	$254.70	$254.70	$254.70
Purchase #5	$104.65	6.722%	$111.6846	$111.68	$111.70	$111.70
Purchase #6	$43.41	5.258%	$45.6925	$45.69	$45.70	$45.70
Purchase #7	$246.50	12.160%	$276.4744	$276.47	$276.45	$276.50
7 purchase totals =	$1,040.79		$1,106.8282	$1,106.81	$1,106.80	$1,106.90