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	$60.89	3.471%	$63.0035	$63.00	$63.00	$63.00
Purchase #2	$19.42	4.513%	$20.2964	$20.30	$20.30	$20.30
Purchase #3	$111.60	10.705%	$123.5468	$123.55	$123.55	$123.50
Purchase #4	$196.59	7.327%	$210.9941	$210.99	$211.00	$211.00
Purchase #5	$126.88	10.416%	$140.0958	$140.10	$140.10	$140.10
Purchase #6	$179.88	5.418%	$189.6259	$189.63	$189.65	$189.60
Purchase #7	$247.63	6.786%	$264.4342	$264.43	$264.45	$264.40
7 purchase totals =	$942.89		$1,011.9967	$1,012.00	$1,012.05	$1,011.90