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	$95.52	8.290%	$103.4386	$103.44	$103.45	$103.40
Purchase #2	$240.49	9.305%	$262.8676	$262.87	$262.85	$262.90
Purchase #3	$224.27	8.550%	$243.4451	$243.45	$243.45	$243.40
Purchase #4	$133.81	10.132%	$147.3676	$147.37	$147.35	$147.40
Purchase #5	$57.50	13.832%	$65.4534	$65.45	$65.45	$65.50
Purchase #6	$200.92	4.102%	$209.1617	$209.16	$209.15	$209.20
Purchase #7	$93.78	11.459%	$104.5263	$104.53	$104.55	$104.50
7 purchase totals =	$1,046.29		$1,136.2603	$1,136.27	$1,136.25	$1,136.30