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	$88.56	3.741%	$91.873	$91.87	$91.85	$91.90
Purchase #2	$117.55	13.436%	$133.344	$133.34	$133.35	$133.30
Purchase #3	$34.46	9.870%	$37.8612	$37.86	$37.85	$37.90
Purchase #4	$129.50	11.845%	$144.8393	$144.84	$144.85	$144.80
Purchase #5	$176.30	13.362%	$199.8572	$199.86	$199.85	$199.90
Purchase #6	$123.38	11.788%	$137.924	$137.92	$137.90	$137.90
Purchase #7	$224.52	8.179%	$242.8835	$242.88	$242.90	$242.90
7 purchase totals =	$894.27		$988.5822	$988.57	$988.55	$988.60