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	$230.90	9.731%	$253.3689	$253.37	$253.35	$253.40
Purchase #2	$79.42	5.165%	$83.522	$83.52	$83.50	$83.50
Purchase #3	$107.61	8.297%	$116.5384	$116.54	$116.55	$116.50
Purchase #4	$149.72	13.555%	$170.0145	$170.01	$170.00	$170.00
Purchase #5	$139.80	3.640%	$144.8887	$144.89	$144.90	$144.90
Purchase #6	$67.40	6.503%	$71.783	$71.78	$71.80	$71.80
Purchase #7	$230.86	11.829%	$258.1684	$258.17	$258.15	$258.20
7 purchase totals =	$1,005.71		$1,098.2839	$1,098.28	$1,098.25	$1,098.30