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	$104.83	5.175%	$110.255	$110.26	$110.25	$110.30
Purchase #2	$131.88	9.382%	$144.253	$144.25	$144.25	$144.30
Purchase #3	$211.49	13.515%	$240.0729	$240.07	$240.05	$240.10
Purchase #4	$46.41	11.105%	$51.5638	$51.56	$51.55	$51.60
Purchase #5	$185.51	12.781%	$209.22	$209.22	$209.20	$209.20
Purchase #6	$48.60	7.387%	$52.1901	$52.19	$52.20	$52.20
Purchase #7	$83.67	6.867%	$89.4156	$89.42	$89.40	$89.40
7 purchase totals =	$812.39		$896.9704	$896.97	$896.90	$897.10