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	$164.80	7.124%	$176.5404	$176.54	$176.55	$176.50
Purchase #2	$78.66	13.436%	$89.2288	$89.23	$89.25	$89.20
Purchase #3	$250.46	4.738%	$262.3268	$262.33	$262.35	$262.30
Purchase #4	$31.90	5.480%	$33.6481	$33.65	$33.65	$33.60
Purchase #5	$172.96	11.247%	$192.4128	$192.41	$192.40	$192.40
Purchase #6	$34.98	8.494%	$37.9512	$37.95	$37.95	$38.00
Purchase #7	$164.77	6.585%	$175.6201	$175.62	$175.60	$175.60
7 purchase totals =	$898.53		$967.7282	$967.73	$967.75	$967.60