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	$62.42	7.420%	$67.0516	$67.05	$67.05	$67.10
Purchase #2	$187.43	3.598%	$194.1737	$194.17	$194.15	$194.20
Purchase #3	$162.96	10.736%	$180.4554	$180.46	$180.45	$180.50
Purchase #4	$88.36	13.550%	$100.3328	$100.33	$100.35	$100.30
Purchase #5	$136.39	12.812%	$153.8643	$153.86	$153.85	$153.90
Purchase #6	$102.95	13.736%	$117.0912	$117.09	$117.10	$117.10
Purchase #7	$21.54	13.862%	$24.5259	$24.53	$24.55	$24.50
7 purchase totals =	$762.05		$837.4949	$837.49	$837.50	$837.60