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	$32.34	10.188%	$35.6348	$35.63	$35.65	$35.60
Purchase #2	$83.75	7.800%	$90.2825	$90.28	$90.30	$90.30
Purchase #3	$238.48	7.207%	$255.6673	$255.67	$255.65	$255.70
Purchase #4	$235.90	8.215%	$255.2792	$255.28	$255.30	$255.30
Purchase #5	$6.37	10.682%	$7.0504	$7.05	$7.05	$7.10
Purchase #6	$116.61	3.378%	$120.5491	$120.55	$120.55	$120.50
Purchase #7	$102.49	5.862%	$108.498	$108.50	$108.50	$108.50
7 purchase totals =	$815.94		$872.9613	$872.96	$873.00	$873.00