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	$121.82	5.192%	$128.1449	$128.14	$128.15	$128.10
Purchase #2	$113.66	8.629%	$123.4677	$123.47	$123.45	$123.50
Purchase #3	$210.59	5.733%	$222.6631	$222.66	$222.65	$222.70
Purchase #4	$19.92	8.418%	$21.5969	$21.60	$21.60	$21.60
Purchase #5	$111.98	5.301%	$117.9161	$117.92	$117.90	$117.90
Purchase #6	$227.48	8.742%	$247.3663	$247.37	$247.35	$247.40
Purchase #7	$235.84	9.543%	$258.3462	$258.35	$258.35	$258.30
7 purchase totals =	$1,041.29		$1,119.5012	$1,119.51	$1,119.45	$1,119.50