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	$237.40	6.760%	$253.4482	$253.45	$253.45	$253.40
Purchase #2	$156.85	10.191%	$172.8346	$172.83	$172.85	$172.80
Purchase #3	$33.83	6.383%	$35.9894	$35.99	$36.00	$36.00
Purchase #4	$39.88	9.629%	$43.72	$43.72	$43.70	$43.70
Purchase #5	$188.34	4.401%	$196.6288	$196.63	$196.65	$196.60
Purchase #6	$105.85	7.542%	$113.8332	$113.83	$113.85	$113.80
Purchase #7	$227.59	10.117%	$250.6153	$250.62	$250.60	$250.60
7 purchase totals =	$989.74		$1,067.0695	$1,067.07	$1,067.10	$1,066.90