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	$38.50	5.315%	$40.5463	$40.55	$40.55	$40.50
Purchase #2	$207.45	5.699%	$219.2726	$219.27	$219.25	$219.30
Purchase #3	$126.53	6.143%	$134.3027	$134.30	$134.30	$134.30
Purchase #4	$18.55	5.366%	$19.5454	$19.55	$19.55	$19.50
Purchase #5	$151.46	13.177%	$171.4179	$171.42	$171.40	$171.40
Purchase #6	$33.96	4.398%	$35.4536	$35.45	$35.45	$35.50
Purchase #7	$149.50	10.681%	$165.4681	$165.47	$165.45	$165.50
7 purchase totals =	$725.95		$786.0066	$786.01	$785.95	$786.00