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	$111.69	7.261%	$119.7998	$119.80	$119.80	$119.80
Purchase #2	$66.41	12.170%	$74.4921	$74.49	$74.50	$74.50
Purchase #3	$173.47	12.298%	$194.8033	$194.80	$194.80	$194.80
Purchase #4	$35.28	7.315%	$37.8607	$37.86	$37.85	$37.90
Purchase #5	$157.38	13.871%	$179.2102	$179.21	$179.20	$179.20
Purchase #6	$152.83	7.659%	$164.5352	$164.54	$164.55	$164.50
Purchase #7	$42.52	12.447%	$47.8125	$47.81	$47.80	$47.80
7 purchase totals =	$739.58		$818.5138	$818.51	$818.50	$818.50