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	$55.26	10.546%	$61.0877	$61.09	$61.10	$61.10
Purchase #2	$167.46	9.156%	$182.7926	$182.79	$182.80	$182.80
Purchase #3	$156.54	5.296%	$164.8304	$164.83	$164.85	$164.80
Purchase #4	$126.67	13.499%	$143.7692	$143.77	$143.75	$143.80
Purchase #5	$33.38	11.443%	$37.1997	$37.20	$37.20	$37.20
Purchase #6	$117.43	13.472%	$133.2502	$133.25	$133.25	$133.30
Purchase #7	$239.82	8.138%	$259.3366	$259.34	$259.35	$259.30
7 purchase totals =	$896.56		$982.2664	$982.27	$982.30	$982.30