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	$90.69	13.823%	$103.2261	$103.23	$103.25	$103.20
Purchase #2	$23.83	7.134%	$25.53	$25.53	$25.55	$25.50
Purchase #3	$95.44	4.786%	$100.0078	$100.01	$100.00	$100.00
Purchase #4	$133.46	12.617%	$150.2986	$150.30	$150.30	$150.30
Purchase #5	$238.66	8.461%	$258.853	$258.85	$258.85	$258.90
Purchase #6	$70.94	7.441%	$76.2186	$76.22	$76.20	$76.20
Purchase #7	$211.56	8.283%	$229.0835	$229.08	$229.10	$229.10
7 purchase totals =	$864.58		$943.2176	$943.22	$943.25	$943.20