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	$22.72	13.192%	$25.7172	$25.72	$25.70	$25.70
Purchase #2	$175.53	10.779%	$194.4504	$194.45	$194.45	$194.50
Purchase #3	$90.37	10.204%	$99.5914	$99.59	$99.60	$99.60
Purchase #4	$215.35	9.260%	$235.2914	$235.29	$235.30	$235.30
Purchase #5	$229.72	6.810%	$245.3639	$245.36	$245.35	$245.40
Purchase #6	$139.83	11.847%	$156.3957	$156.40	$156.40	$156.40
Purchase #7	$178.73	8.174%	$193.3394	$193.34	$193.35	$193.30
7 purchase totals =	$1,052.25		$1,150.1494	$1,150.15	$1,150.15	$1,150.20