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	$29.91	11.305%	$33.2913	$33.29	$33.30	$33.30
Purchase #2	$147.57	11.371%	$164.3502	$164.35	$164.35	$164.40
Purchase #3	$184.33	11.677%	$205.8542	$205.85	$205.85	$205.90
Purchase #4	$28.69	4.255%	$29.9108	$29.91	$29.90	$29.90
Purchase #5	$124.37	7.554%	$133.7649	$133.76	$133.75	$133.80
Purchase #6	$28.92	8.803%	$31.4658	$31.47	$31.45	$31.50
Purchase #7	$137.85	11.362%	$153.5125	$153.51	$153.50	$153.50
7 purchase totals =	$681.64		$752.1497	$752.14	$752.10	$752.30