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	$191.55	3.614%	$198.4726	$198.47	$198.45	$198.50
Purchase #2	$111.68	4.649%	$116.872	$116.87	$116.85	$116.90
Purchase #3	$34.80	11.348%	$38.7491	$38.75	$38.75	$38.70
Purchase #4	$179.95	4.711%	$188.4274	$188.43	$188.45	$188.40
Purchase #5	$99.55	7.695%	$107.2104	$107.21	$107.20	$107.20
Purchase #6	$64.68	11.332%	$72.0095	$72.01	$72.00	$72.00
Purchase #7	$30.31	11.470%	$33.7866	$33.79	$33.80	$33.80
7 purchase totals =	$712.52		$755.5276	$755.53	$755.50	$755.50