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	$214.83	7.825%	$231.6404	$231.64	$231.65	$231.60
Purchase #2	$83.82	12.759%	$94.5146	$94.51	$94.50	$94.50
Purchase #3	$133.54	6.477%	$142.1894	$142.19	$142.20	$142.20
Purchase #4	$37.71	6.754%	$40.2569	$40.26	$40.25	$40.30
Purchase #5	$227.45	8.476%	$246.7287	$246.73	$246.75	$246.70
Purchase #6	$58.52	13.813%	$66.6034	$66.60	$66.60	$66.60
Purchase #7	$206.54	11.293%	$229.8646	$229.86	$229.85	$229.90
7 purchase totals =	$962.41		$1,051.7980	$1,051.79	$1,051.80	$1,051.80