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	$136.36	7.106%	$146.0497	$146.05	$146.05	$146.00
Purchase #2	$33.28	4.116%	$34.6498	$34.65	$34.65	$34.60
Purchase #3	$164.99	5.145%	$173.4787	$173.48	$173.50	$173.50
Purchase #4	$36.59	6.131%	$38.8333	$38.83	$38.85	$38.80
Purchase #5	$131.48	9.437%	$143.8878	$143.89	$143.90	$143.90
Purchase #6	$109.89	12.712%	$123.8592	$123.86	$123.85	$123.90
Purchase #7	$94.90	12.107%	$106.3895	$106.39	$106.40	$106.40
7 purchase totals =	$707.49		$767.1480	$767.15	$767.20	$767.10