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	$223.92	11.481%	$249.6283	$249.63	$249.65	$249.60
Purchase #2	$205.28	10.585%	$227.0089	$227.01	$227.00	$227.00
Purchase #3	$193.39	3.365%	$199.8976	$199.90	$199.90	$199.90
Purchase #4	$56.66	8.574%	$61.518	$61.52	$61.50	$61.50
Purchase #5	$58.35	11.779%	$65.223	$65.22	$65.20	$65.20
Purchase #6	$134.90	6.831%	$144.115	$144.12	$144.10	$144.10
Purchase #7	$55.65	7.517%	$59.8332	$59.83	$59.85	$59.80
7 purchase totals =	$928.15		$1,007.2240	$1,007.23	$1,007.20	$1,007.10