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	$232.59	3.584%	$240.926	$240.93	$240.95	$240.90
Purchase #2	$63.76	3.477%	$65.9769	$65.98	$66.00	$66.00
Purchase #3	$118.84	9.475%	$130.1001	$130.10	$130.10	$130.10
Purchase #4	$123.66	5.647%	$130.6431	$130.64	$130.65	$130.60
Purchase #5	$189.42	10.578%	$209.4568	$209.46	$209.45	$209.50
Purchase #6	$192.95	13.800%	$219.5771	$219.58	$219.60	$219.60
Purchase #7	$139.30	7.861%	$150.2504	$150.25	$150.25	$150.30
7 purchase totals =	$1,060.52		$1,146.9304	$1,146.94	$1,147.00	$1,147.00