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	$228.61	5.331%	$240.7972	$240.80	$240.80	$240.80
Purchase #2	$235.85	8.800%	$256.6048	$256.60	$256.60	$256.60
Purchase #3	$126.75	5.308%	$133.4779	$133.48	$133.50	$133.50
Purchase #4	$157.71	9.633%	$172.9022	$172.90	$172.90	$172.90
Purchase #5	$144.38	5.697%	$152.6053	$152.61	$152.60	$152.60
Purchase #6	$64.54	8.304%	$69.8994	$69.90	$69.90	$69.90
Purchase #7	$23.51	6.409%	$25.0168	$25.02	$25.00	$25.00
7 purchase totals =	$981.35		$1,051.3036	$1,051.31	$1,051.30	$1,051.30