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	$184.28	6.699%	$196.6249	$196.62	$196.60	$196.60
Purchase #2	$30.64	5.679%	$32.38	$32.38	$32.40	$32.40
Purchase #3	$237.26	7.109%	$254.1268	$254.13	$254.15	$254.10
Purchase #4	$183.25	12.681%	$206.4879	$206.49	$206.50	$206.50
Purchase #5	$158.88	13.256%	$179.9411	$179.94	$179.95	$179.90
Purchase #6	$16.32	3.457%	$16.8842	$16.88	$16.90	$16.90
Purchase #7	$200.89	11.169%	$223.3274	$223.33	$223.35	$223.30
7 purchase totals =	$1,011.52		$1,109.7723	$1,109.77	$1,109.85	$1,109.70