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	$115.38	10.795%	$127.8353	$127.84	$127.85	$127.80
Purchase #2	$25.42	11.220%	$28.2721	$28.27	$28.25	$28.30
Purchase #3	$52.86	9.444%	$57.8521	$57.85	$57.85	$57.90
Purchase #4	$37.62	8.400%	$40.7801	$40.78	$40.80	$40.80
Purchase #5	$227.28	5.121%	$238.919	$238.92	$238.90	$238.90
Purchase #6	$34.70	6.116%	$36.8223	$36.82	$36.80	$36.80
Purchase #7	$250.49	5.363%	$263.9238	$263.92	$263.90	$263.90
7 purchase totals =	$743.75		$794.4047	$794.40	$794.35	$794.40