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	$249.76	4.620%	$261.2989	$261.30	$261.30	$261.30
Purchase #2	$64.65	11.618%	$72.161	$72.16	$72.15	$72.20
Purchase #3	$43.98	6.776%	$46.9601	$46.96	$46.95	$47.00
Purchase #4	$18.95	13.253%	$21.4614	$21.46	$21.45	$21.50
Purchase #5	$175.73	4.402%	$183.4656	$183.47	$183.45	$183.50
Purchase #6	$34.40	12.203%	$38.5978	$38.60	$38.60	$38.60
Purchase #7	$89.88	12.692%	$101.2876	$101.29	$101.30	$101.30
7 purchase totals =	$677.35		$725.2324	$725.24	$725.20	$725.40