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	$38.29	8.723%	$41.63	$41.63	$41.65	$41.60
Purchase #2	$32.85	8.431%	$35.6196	$35.62	$35.60	$35.60
Purchase #3	$25.73	10.342%	$28.391	$28.39	$28.40	$28.40
Purchase #4	$192.54	12.265%	$216.155	$216.16	$216.15	$216.20
Purchase #5	$82.55	11.758%	$92.2562	$92.26	$92.25	$92.30
Purchase #6	$136.27	6.147%	$144.6465	$144.65	$144.65	$144.60
Purchase #7	$221.83	9.778%	$243.5205	$243.52	$243.50	$243.50
7 purchase totals =	$730.06		$802.2188	$802.23	$802.20	$802.20