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	$130.70	8.585%	$141.9206	$141.92	$141.90	$141.90
Purchase #2	$18.54	4.503%	$19.3749	$19.37	$19.35	$19.40
Purchase #3	$167.71	7.832%	$180.845	$180.85	$180.85	$180.80
Purchase #4	$152.27	3.322%	$157.3284	$157.33	$157.35	$157.30
Purchase #5	$51.59	11.374%	$57.4578	$57.46	$57.45	$57.50
Purchase #6	$223.60	11.561%	$249.4504	$249.45	$249.45	$249.50
Purchase #7	$180.27	5.487%	$190.1614	$190.16	$190.15	$190.20
7 purchase totals =	$924.68		$996.5385	$996.54	$996.50	$996.60