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	$161.30	6.585%	$171.9216	$171.92	$171.90	$171.90
Purchase #2	$186.37	5.249%	$196.1526	$196.15	$196.15	$196.20
Purchase #3	$136.83	7.254%	$146.7556	$146.76	$146.75	$146.80
Purchase #4	$79.28	10.496%	$87.6012	$87.60	$87.60	$87.60
Purchase #5	$153.90	13.444%	$174.5903	$174.59	$174.60	$174.60
Purchase #6	$134.48	8.602%	$146.048	$146.05	$146.05	$146.00
Purchase #7	$223.30	13.564%	$253.5884	$253.59	$253.60	$253.60
7 purchase totals =	$1,075.46		$1,176.6577	$1,176.66	$1,176.65	$1,176.70