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	$66.55	9.675%	$72.9887	$72.99	$73.00	$73.00
Purchase #2	$24.82	11.675%	$27.7177	$27.72	$27.70	$27.70
Purchase #3	$205.58	8.749%	$223.5662	$223.57	$223.55	$223.60
Purchase #4	$40.30	3.276%	$41.6202	$41.62	$41.60	$41.60
Purchase #5	$200.84	4.425%	$209.7272	$209.73	$209.75	$209.70
Purchase #6	$111.61	10.431%	$123.252	$123.25	$123.25	$123.30
Purchase #7	$35.99	12.225%	$40.3898	$40.39	$40.40	$40.40
7 purchase totals =	$685.69		$739.2618	$739.27	$739.25	$739.30