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	$241.89	3.398%	$250.1094	$250.11	$250.10	$250.10
Purchase #2	$240.88	4.595%	$251.9484	$251.95	$251.95	$251.90
Purchase #3	$180.62	9.335%	$197.4809	$197.48	$197.50	$197.50
Purchase #4	$87.82	13.270%	$99.4737	$99.47	$99.45	$99.50
Purchase #5	$86.54	11.521%	$96.5103	$96.51	$96.50	$96.50
Purchase #6	$33.92	8.371%	$36.7594	$36.76	$36.75	$36.80
Purchase #7	$117.44	4.772%	$123.0442	$123.04	$123.05	$123.00
7 purchase totals =	$989.11		$1,055.3263	$1,055.32	$1,055.30	$1,055.30