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	$133.56	9.659%	$146.4606	$146.46	$146.45	$146.50
Purchase #2	$43.66	8.822%	$47.5117	$47.51	$47.50	$47.50
Purchase #3	$7.41	4.186%	$7.7202	$7.72	$7.70	$7.70
Purchase #4	$99.31	13.722%	$112.9373	$112.94	$112.95	$112.90
Purchase #5	$181.77	4.349%	$189.6752	$189.68	$189.70	$189.70
Purchase #6	$31.69	4.530%	$33.1256	$33.13	$33.15	$33.10
Purchase #7	$104.87	10.212%	$115.5793	$115.58	$115.60	$115.60
7 purchase totals =	$602.27		$653.0099	$653.02	$653.05	$653.00