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	$129.94	3.800%	$134.8777	$134.88	$134.90	$134.90
Purchase #2	$90.90	10.667%	$100.5963	$100.60	$100.60	$100.60
Purchase #3	$79.61	10.261%	$87.7788	$87.78	$87.80	$87.80
Purchase #4	$168.34	5.231%	$177.1459	$177.15	$177.15	$177.10
Purchase #5	$118.41	4.126%	$123.2956	$123.30	$123.30	$123.30
Purchase #6	$150.65	7.428%	$161.8403	$161.84	$161.85	$161.80
Purchase #7	$195.30	11.356%	$217.4783	$217.48	$217.50	$217.50
7 purchase totals =	$933.15		$1,003.0129	$1,003.03	$1,003.10	$1,003.00