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	$10.89	8.585%	$11.8249	$11.82	$11.80	$11.80
Purchase #2	$41.29	11.458%	$46.021	$46.02	$46.00	$46.00
Purchase #3	$82.33	4.468%	$86.0085	$86.01	$86.00	$86.00
Purchase #4	$168.89	12.754%	$190.4302	$190.43	$190.45	$190.40
Purchase #5	$230.45	5.136%	$242.2859	$242.29	$242.30	$242.30
Purchase #6	$189.40	11.414%	$211.0181	$211.02	$211.00	$211.00
Purchase #7	$35.30	8.160%	$38.1805	$38.18	$38.20	$38.20
7 purchase totals =	$758.55		$825.7691	$825.77	$825.75	$825.70