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	$78.79	6.543%	$83.9452	$83.95	$83.95	$83.90
Purchase #2	$161.28	13.757%	$183.4673	$183.47	$183.45	$183.50
Purchase #3	$199.97	10.444%	$220.8549	$220.85	$220.85	$220.90
Purchase #4	$104.52	6.292%	$111.0964	$111.10	$111.10	$111.10
Purchase #5	$154.46	7.114%	$165.4483	$165.45	$165.45	$165.40
Purchase #6	$147.48	6.167%	$156.5751	$156.58	$156.60	$156.60
Purchase #7	$109.26	6.169%	$116.0002	$116.00	$116.00	$116.00
7 purchase totals =	$955.76		$1,037.3874	$1,037.40	$1,037.40	$1,037.40