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	$81.80	6.837%	$87.3927	$87.39	$87.40	$87.40
Purchase #2	$32.68	7.567%	$35.1529	$35.15	$35.15	$35.20
Purchase #3	$78.41	8.863%	$85.3595	$85.36	$85.35	$85.40
Purchase #4	$136.61	4.768%	$143.1236	$143.12	$143.10	$143.10
Purchase #5	$113.74	5.296%	$119.7637	$119.76	$119.75	$119.80
Purchase #6	$134.83	10.184%	$148.5611	$148.56	$148.55	$148.60
Purchase #7	$104.78	8.104%	$113.2714	$113.27	$113.25	$113.30
7 purchase totals =	$682.85		$732.6249	$732.61	$732.55	$732.80