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	$249.32	5.176%	$262.2248	$262.22	$262.20	$262.20
Purchase #2	$107.86	11.261%	$120.0061	$120.01	$120.00	$120.00
Purchase #3	$169.61	10.793%	$187.916	$187.92	$187.90	$187.90
Purchase #4	$205.84	13.249%	$233.1117	$233.11	$233.10	$233.10
Purchase #5	$185.77	5.395%	$195.7923	$195.79	$195.80	$195.80
Purchase #6	$108.73	13.434%	$123.3368	$123.34	$123.35	$123.30
Purchase #7	$87.73	13.566%	$99.6315	$99.63	$99.65	$99.60
7 purchase totals =	$1,114.86		$1,222.0192	$1,222.02	$1,222.00	$1,221.90