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	$109.58	8.380%	$118.7628	$118.76	$118.75	$118.80
Purchase #2	$65.54	11.136%	$72.8385	$72.84	$72.85	$72.80
Purchase #3	$74.76	6.289%	$79.4617	$79.46	$79.45	$79.50
Purchase #4	$144.95	7.574%	$155.9285	$155.93	$155.95	$155.90
Purchase #5	$91.31	3.243%	$94.2712	$94.27	$94.25	$94.30
Purchase #6	$154.34	9.238%	$168.5979	$168.60	$168.60	$168.60
Purchase #7	$145.50	8.318%	$157.6027	$157.60	$157.60	$157.60
7 purchase totals =	$785.98		$847.4633	$847.46	$847.45	$847.50