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	$115.93	11.118%	$128.8191	$128.82	$128.80	$128.80
Purchase #2	$10.81	3.443%	$11.1822	$11.18	$11.20	$11.20
Purchase #3	$41.82	4.400%	$43.6601	$43.66	$43.65	$43.70
Purchase #4	$135.86	5.686%	$143.585	$143.59	$143.60	$143.60
Purchase #5	$84.73	11.269%	$94.2782	$94.28	$94.30	$94.30
Purchase #6	$184.57	7.531%	$198.47	$198.47	$198.45	$198.50
Purchase #7	$166.77	12.408%	$187.4628	$187.46	$187.45	$187.50
7 purchase totals =	$740.49		$807.4574	$807.46	$807.45	$807.60