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	$188.80	3.761%	$195.9008	$195.90	$195.90	$195.90
Purchase #2	$9.36	7.457%	$10.058	$10.06	$10.05	$10.10
Purchase #3	$77.59	7.808%	$83.6482	$83.65	$83.65	$83.60
Purchase #4	$12.25	11.201%	$13.6221	$13.62	$13.60	$13.60
Purchase #5	$151.40	9.455%	$165.7149	$165.71	$165.70	$165.70
Purchase #6	$11.59	11.327%	$12.9028	$12.90	$12.90	$12.90
Purchase #7	$72.25	10.480%	$79.8218	$79.82	$79.80	$79.80
7 purchase totals =	$523.24		$561.6686	$561.66	$561.60	$561.60