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	$128.75	4.379%	$134.388	$134.39	$134.40	$134.40
Purchase #2	$168.52	6.690%	$179.794	$179.79	$179.80	$179.80
Purchase #3	$186.35	7.776%	$200.8406	$200.84	$200.85	$200.80
Purchase #4	$23.62	9.707%	$25.9128	$25.91	$25.90	$25.90
Purchase #5	$233.92	4.516%	$244.4838	$244.48	$244.50	$244.50
Purchase #6	$141.66	3.700%	$146.9014	$146.90	$146.90	$146.90
Purchase #7	$49.71	7.577%	$53.4765	$53.48	$53.50	$53.50
7 purchase totals =	$932.53		$985.7971	$985.79	$985.85	$985.80