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	$128.89	8.291%	$139.5763	$139.58	$139.60	$139.60
Purchase #2	$197.52	7.129%	$211.6012	$211.60	$211.60	$211.60
Purchase #3	$135.94	5.630%	$143.5934	$143.59	$143.60	$143.60
Purchase #4	$160.55	11.539%	$179.0759	$179.08	$179.10	$179.10
Purchase #5	$108.95	3.817%	$113.1086	$113.11	$113.10	$113.10
Purchase #6	$145.75	12.616%	$164.1378	$164.14	$164.15	$164.10
Purchase #7	$104.78	11.428%	$116.7543	$116.75	$116.75	$116.80
7 purchase totals =	$982.38		$1,067.8475	$1,067.85	$1,067.90	$1,067.90