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	$165.41	12.371%	$185.8729	$185.87	$185.85	$185.90
Purchase #2	$14.61	12.714%	$16.4675	$16.47	$16.45	$16.50
Purchase #3	$110.68	11.374%	$123.2687	$123.27	$123.25	$123.30
Purchase #4	$57.32	7.303%	$61.5061	$61.51	$61.50	$61.50
Purchase #5	$83.36	4.369%	$87.002	$87.00	$87.00	$87.00
Purchase #6	$17.94	3.290%	$18.5302	$18.53	$18.55	$18.50
Purchase #7	$41.78	11.520%	$46.5931	$46.59	$46.60	$46.60
7 purchase totals =	$491.10		$539.2405	$539.24	$539.20	$539.30