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	$91.92	8.204%	$99.4611	$99.46	$99.45	$99.50
Purchase #2	$151.39	11.658%	$169.039	$169.04	$169.05	$169.00
Purchase #3	$186.26	7.453%	$200.142	$200.14	$200.15	$200.10
Purchase #4	$87.75	10.227%	$96.7242	$96.72	$96.70	$96.70
Purchase #5	$171.27	10.728%	$189.6438	$189.64	$189.65	$189.60
Purchase #6	$214.40	12.606%	$241.4273	$241.43	$241.45	$241.40
Purchase #7	$146.92	3.466%	$152.0122	$152.01	$152.00	$152.00
7 purchase totals =	$1,049.91		$1,148.4496	$1,148.44	$1,148.45	$1,148.30