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	$198.33	5.210%	$208.663	$208.66	$208.65	$208.70
Purchase #2	$158.58	4.634%	$165.9286	$165.93	$165.95	$165.90
Purchase #3	$164.33	11.623%	$183.4301	$183.43	$183.45	$183.40
Purchase #4	$113.63	4.404%	$118.6343	$118.63	$118.65	$118.60
Purchase #5	$126.73	4.133%	$131.9678	$131.97	$131.95	$132.00
Purchase #6	$41.97	6.297%	$44.6129	$44.61	$44.60	$44.60
Purchase #7	$134.81	11.440%	$150.2323	$150.23	$150.25	$150.20
7 purchase totals =	$938.38		$1,003.4690	$1,003.46	$1,003.50	$1,003.40