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	$83.53	3.733%	$86.6482	$86.65	$86.65	$86.60
Purchase #2	$95.76	9.513%	$104.8696	$104.87	$104.85	$104.90
Purchase #3	$32.93	5.196%	$34.641	$34.64	$34.65	$34.60
Purchase #4	$134.58	3.573%	$139.3885	$139.39	$139.40	$139.40
Purchase #5	$82.54	6.746%	$88.1081	$88.11	$88.10	$88.10
Purchase #6	$69.88	10.664%	$77.332	$77.33	$77.35	$77.30
Purchase #7	$79.31	13.868%	$90.3087	$90.31	$90.30	$90.30
7 purchase totals =	$578.53		$621.2961	$621.30	$621.30	$621.20