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	$95.87	4.350%	$100.0403	$100.04	$100.05	$100.00
Purchase #2	$76.90	12.175%	$86.2626	$86.26	$86.25	$86.30
Purchase #3	$190.58	13.559%	$216.4207	$216.42	$216.40	$216.40
Purchase #4	$139.31	13.619%	$158.2826	$158.28	$158.30	$158.30
Purchase #5	$113.66	11.333%	$126.5411	$126.54	$126.55	$126.50
Purchase #6	$128.33	13.788%	$146.0241	$146.02	$146.00	$146.00
Purchase #7	$175.39	9.738%	$192.4695	$192.47	$192.45	$192.50
7 purchase totals =	$920.04		$1,026.0409	$1,026.03	$1,026.00	$1,026.00