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	$95.70	8.736%	$104.0604	$104.06	$104.05	$104.10
Purchase #2	$59.25	3.759%	$61.4772	$61.48	$61.50	$61.50
Purchase #3	$220.57	10.620%	$243.9945	$243.99	$244.00	$244.00
Purchase #4	$51.57	12.136%	$57.8285	$57.83	$57.85	$57.80
Purchase #5	$221.61	8.662%	$240.8059	$240.81	$240.80	$240.80
Purchase #6	$178.52	6.668%	$190.4237	$190.42	$190.40	$190.40
Purchase #7	$56.47	4.447%	$58.9812	$58.98	$59.00	$59.00
7 purchase totals =	$883.69		$957.5714	$957.57	$957.60	$957.60