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	$91.83	5.221%	$96.6244	$96.62	$96.60	$96.60
Purchase #2	$31.35	8.664%	$34.0662	$34.07	$34.05	$34.10
Purchase #3	$12.78	7.214%	$13.7019	$13.70	$13.70	$13.70
Purchase #4	$19.47	12.435%	$21.8911	$21.89	$21.90	$21.90
Purchase #5	$55.59	10.580%	$61.4714	$61.47	$61.45	$61.50
Purchase #6	$106.60	6.480%	$113.5077	$113.51	$113.50	$113.50
Purchase #7	$62.80	3.129%	$64.765	$64.77	$64.75	$64.80
7 purchase totals =	$380.42		$406.0277	$406.03	$405.95	$406.10