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	$100.83	10.709%	$111.6279	$111.63	$111.65	$111.60
Purchase #2	$208.66	9.807%	$229.1233	$229.12	$229.10	$229.10
Purchase #3	$7.34	6.795%	$7.8388	$7.84	$7.85	$7.80
Purchase #4	$33.74	9.768%	$37.0357	$37.04	$37.05	$37.00
Purchase #5	$155.69	12.659%	$175.3988	$175.40	$175.40	$175.40
Purchase #6	$54.86	7.669%	$59.0672	$59.07	$59.05	$59.10
Purchase #7	$214.45	12.111%	$240.422	$240.42	$240.40	$240.40
7 purchase totals =	$775.57		$860.5137	$860.52	$860.50	$860.40