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	$42.70	7.228%	$45.7864	$45.79	$45.80	$45.80
Purchase #2	$28.42	3.349%	$29.3718	$29.37	$29.35	$29.40
Purchase #3	$116.59	3.602%	$120.7896	$120.79	$120.80	$120.80
Purchase #4	$182.73	7.390%	$196.2337	$196.23	$196.25	$196.20
Purchase #5	$113.25	12.410%	$127.3043	$127.30	$127.30	$127.30
Purchase #6	$224.94	4.836%	$235.8181	$235.82	$235.80	$235.80
Purchase #7	$248.72	7.167%	$266.5458	$266.55	$266.55	$266.50
7 purchase totals =	$957.35		$1,021.8497	$1,021.85	$1,021.85	$1,021.80