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	$127.29	7.495%	$136.8304	$136.83	$136.85	$136.80
Purchase #2	$48.66	3.602%	$50.4127	$50.41	$50.40	$50.40
Purchase #3	$136.95	11.162%	$152.2364	$152.24	$152.25	$152.20
Purchase #4	$175.55	8.722%	$190.8615	$190.86	$190.85	$190.90
Purchase #5	$123.63	4.284%	$128.9263	$128.93	$128.95	$128.90
Purchase #6	$238.42	9.250%	$260.4739	$260.47	$260.45	$260.50
Purchase #7	$80.45	13.254%	$91.1128	$91.11	$91.10	$91.10
7 purchase totals =	$930.95		$1,010.8540	$1,010.85	$1,010.85	$1,010.80