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	$208.82	4.516%	$218.2503	$218.25	$218.25	$218.30
Purchase #2	$41.49	11.764%	$46.3709	$46.37	$46.35	$46.40
Purchase #3	$200.61	11.840%	$224.3622	$224.36	$224.35	$224.40
Purchase #4	$162.88	13.624%	$185.0708	$185.07	$185.05	$185.10
Purchase #5	$68.85	13.618%	$78.226	$78.23	$78.25	$78.20
Purchase #6	$216.95	11.279%	$241.4198	$241.42	$241.40	$241.40
Purchase #7	$250.55	12.590%	$282.0942	$282.09	$282.10	$282.10
7 purchase totals =	$1,150.15		$1,275.7942	$1,275.79	$1,275.75	$1,275.90