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	$78.27	4.312%	$81.645	$81.65	$81.65	$81.60
Purchase #2	$90.90	6.132%	$96.474	$96.47	$96.45	$96.50
Purchase #3	$76.64	8.133%	$82.8731	$82.87	$82.85	$82.90
Purchase #4	$128.45	11.803%	$143.611	$143.61	$143.60	$143.60
Purchase #5	$58.86	3.751%	$61.0678	$61.07	$61.05	$61.10
Purchase #6	$10.84	4.247%	$11.3004	$11.30	$11.30	$11.30
Purchase #7	$123.38	12.517%	$138.8235	$138.82	$138.80	$138.80
7 purchase totals =	$567.34		$615.7948	$615.79	$615.70	$615.80