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	$65.58	9.805%	$72.0101	$72.01	$72.00	$72.00
Purchase #2	$85.37	7.584%	$91.8445	$91.84	$91.85	$91.80
Purchase #3	$128.61	12.149%	$144.2348	$144.23	$144.25	$144.20
Purchase #4	$19.59	3.266%	$20.2298	$20.23	$20.25	$20.20
Purchase #5	$146.96	11.638%	$164.0632	$164.06	$164.05	$164.10
Purchase #6	$53.28	12.176%	$59.7674	$59.77	$59.75	$59.80
Purchase #7	$7.53	13.767%	$8.5667	$8.57	$8.55	$8.60
7 purchase totals =	$506.92		$560.7165	$560.71	$560.70	$560.70