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	$139.87	4.615%	$146.325	$146.33	$146.35	$146.30
Purchase #2	$33.83	11.762%	$37.8091	$37.81	$37.80	$37.80
Purchase #3	$49.90	13.666%	$56.7193	$56.72	$56.70	$56.70
Purchase #4	$59.27	9.494%	$64.8971	$64.90	$64.90	$64.90
Purchase #5	$79.97	8.293%	$86.6019	$86.60	$86.60	$86.60
Purchase #6	$5.88	10.765%	$6.513	$6.51	$6.50	$6.50
Purchase #7	$15.57	12.829%	$17.5675	$17.57	$17.55	$17.60
7 purchase totals =	$384.29		$416.4329	$416.44	$416.40	$416.40