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	$189.66	4.847%	$198.8528	$198.85	$198.85	$198.90
Purchase #2	$75.53	12.866%	$85.2477	$85.25	$85.25	$85.20
Purchase #3	$19.56	11.603%	$21.8295	$21.83	$21.85	$21.80
Purchase #4	$168.30	7.298%	$180.5825	$180.58	$180.60	$180.60
Purchase #5	$33.64	5.135%	$35.3674	$35.37	$35.35	$35.40
Purchase #6	$80.67	3.288%	$83.3224	$83.32	$83.30	$83.30
Purchase #7	$6.71	6.342%	$7.1355	$7.14	$7.15	$7.10
7 purchase totals =	$574.07		$612.3378	$612.34	$612.35	$612.30