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	$76.88	11.537%	$85.7496	$85.75	$85.75	$85.70
Purchase #2	$236.96	4.126%	$246.737	$246.74	$246.75	$246.70
Purchase #3	$209.27	9.665%	$229.4959	$229.50	$229.50	$229.50
Purchase #4	$172.64	8.674%	$187.6148	$187.61	$187.60	$187.60
Purchase #5	$136.81	12.472%	$153.8729	$153.87	$153.85	$153.90
Purchase #6	$137.51	13.808%	$156.4974	$156.50	$156.50	$156.50
Purchase #7	$230.86	4.312%	$240.8147	$240.81	$240.80	$240.80
7 purchase totals =	$1,200.93		$1,300.7823	$1,300.78	$1,300.75	$1,300.70