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	$69.94	3.602%	$72.4592	$72.46	$72.45	$72.50
Purchase #2	$172.66	7.125%	$184.962	$184.96	$184.95	$185.00
Purchase #3	$241.26	11.269%	$268.4476	$268.45	$268.45	$268.40
Purchase #4	$183.25	7.377%	$196.7684	$196.77	$196.75	$196.80
Purchase #5	$145.92	4.789%	$152.9081	$152.91	$152.90	$152.90
Purchase #6	$167.42	10.614%	$185.19	$185.19	$185.20	$185.20
Purchase #7	$183.29	7.625%	$197.2659	$197.27	$197.25	$197.30
7 purchase totals =	$1,163.74		$1,258.0012	$1,258.01	$1,257.95	$1,258.10