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	$85.80	5.531%	$90.5456	$90.55	$90.55	$90.50
Purchase #2	$14.76	13.245%	$16.715	$16.72	$16.70	$16.70
Purchase #3	$54.58	9.685%	$59.8661	$59.87	$59.85	$59.90
Purchase #4	$139.47	11.781%	$155.901	$155.90	$155.90	$155.90
Purchase #5	$107.52	10.115%	$118.3956	$118.40	$118.40	$118.40
Purchase #6	$13.39	7.666%	$14.4165	$14.42	$14.40	$14.40
Purchase #7	$206.63	5.747%	$218.505	$218.51	$218.50	$218.50
7 purchase totals =	$622.15		$674.3448	$674.37	$674.30	$674.30