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	$203.84	10.525%	$225.2942	$225.29	$225.30	$225.30
Purchase #2	$238.27	8.433%	$258.3633	$258.36	$258.35	$258.40
Purchase #3	$93.53	6.367%	$99.4851	$99.49	$99.50	$99.50
Purchase #4	$30.51	8.138%	$32.9929	$32.99	$33.00	$33.00
Purchase #5	$165.55	5.416%	$174.5162	$174.52	$174.50	$174.50
Purchase #6	$62.76	4.452%	$65.5541	$65.55	$65.55	$65.60
Purchase #7	$92.87	8.341%	$100.6163	$100.62	$100.60	$100.60
7 purchase totals =	$887.33		$956.8221	$956.82	$956.80	$956.90