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	$247.65	11.255%	$275.523	$275.52	$275.50	$275.50
Purchase #2	$209.78	11.296%	$233.4767	$233.48	$233.50	$233.50
Purchase #3	$34.85	4.513%	$36.4228	$36.42	$36.40	$36.40
Purchase #4	$29.84	3.633%	$30.9241	$30.92	$30.90	$30.90
Purchase #5	$222.62	13.402%	$252.4555	$252.46	$252.45	$252.50
Purchase #6	$104.78	12.527%	$117.9058	$117.91	$117.90	$117.90
Purchase #7	$92.96	8.142%	$100.5288	$100.53	$100.55	$100.50
7 purchase totals =	$942.48		$1,047.2367	$1,047.24	$1,047.20	$1,047.20