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	$76.59	11.470%	$85.3749	$85.37	$85.35	$85.40
Purchase #2	$125.59	4.850%	$131.6811	$131.68	$131.70	$131.70
Purchase #3	$144.72	8.375%	$156.8403	$156.84	$156.85	$156.80
Purchase #4	$192.52	3.145%	$198.5748	$198.57	$198.55	$198.60
Purchase #5	$243.50	5.729%	$257.4501	$257.45	$257.45	$257.50
Purchase #6	$164.64	4.587%	$172.192	$172.19	$172.20	$172.20
Purchase #7	$140.41	3.624%	$145.4985	$145.50	$145.50	$145.50
7 purchase totals =	$1,087.97		$1,147.6117	$1,147.60	$1,147.60	$1,147.70