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	$90.44	4.779%	$94.7621	$94.76	$94.75	$94.80
Purchase #2	$118.73	13.658%	$134.9461	$134.95	$134.95	$134.90
Purchase #3	$148.85	3.759%	$154.4453	$154.45	$154.45	$154.40
Purchase #4	$29.38	7.385%	$31.5497	$31.55	$31.55	$31.50
Purchase #5	$27.60	3.753%	$28.6358	$28.64	$28.65	$28.60
Purchase #6	$34.78	3.182%	$35.8867	$35.89	$35.90	$35.90
Purchase #7	$84.71	12.679%	$95.4504	$95.45	$95.45	$95.50
7 purchase totals =	$534.49		$575.6761	$575.69	$575.70	$575.60