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	$94.66	4.349%	$98.7768	$98.78	$98.80	$98.80
Purchase #2	$199.72	3.150%	$206.0112	$206.01	$206.00	$206.00
Purchase #3	$180.61	10.322%	$199.2526	$199.25	$199.25	$199.30
Purchase #4	$76.44	5.523%	$80.6618	$80.66	$80.65	$80.70
Purchase #5	$108.61	5.730%	$114.8334	$114.83	$114.85	$114.80
Purchase #6	$118.37	11.498%	$131.9802	$131.98	$132.00	$132.00
Purchase #7	$151.59	13.312%	$171.7697	$171.77	$171.75	$171.80
7 purchase totals =	$930.00		$1,003.2857	$1,003.28	$1,003.30	$1,003.40