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	$54.42	7.759%	$58.6424	$58.64	$58.65	$58.60
Purchase #2	$29.99	6.397%	$31.9085	$31.91	$31.90	$31.90
Purchase #3	$170.70	8.671%	$185.5014	$185.50	$185.50	$185.50
Purchase #4	$132.78	7.117%	$142.23	$142.23	$142.25	$142.20
Purchase #5	$58.35	4.769%	$61.1327	$61.13	$61.15	$61.10
Purchase #6	$28.57	10.550%	$31.5841	$31.58	$31.60	$31.60
Purchase #7	$87.71	7.692%	$94.4567	$94.46	$94.45	$94.50
7 purchase totals =	$562.52		$605.4558	$605.45	$605.50	$605.40