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	$183.36	9.195%	$200.22	$200.22	$200.20	$200.20
Purchase #2	$189.85	10.793%	$210.3405	$210.34	$210.35	$210.30
Purchase #3	$130.66	10.770%	$144.7321	$144.73	$144.75	$144.70
Purchase #4	$209.43	13.745%	$238.2162	$238.22	$238.20	$238.20
Purchase #5	$90.76	12.294%	$101.918	$101.92	$101.90	$101.90
Purchase #6	$42.30	10.109%	$46.5761	$46.58	$46.60	$46.60
Purchase #7	$24.72	3.389%	$25.5578	$25.56	$25.55	$25.60
7 purchase totals =	$871.08		$967.5607	$967.57	$967.55	$967.50