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	$193.77	6.578%	$206.5162	$206.52	$206.50	$206.50
Purchase #2	$92.78	11.297%	$103.2614	$103.26	$103.25	$103.30
Purchase #3	$18.97	3.660%	$19.6643	$19.66	$19.65	$19.70
Purchase #4	$130.44	13.154%	$147.5981	$147.60	$147.60	$147.60
Purchase #5	$39.26	13.470%	$44.5483	$44.55	$44.55	$44.50
Purchase #6	$36.25	4.563%	$37.9041	$37.90	$37.90	$37.90
Purchase #7	$246.63	3.531%	$255.3385	$255.34	$255.35	$255.30
7 purchase totals =	$758.10		$814.8309	$814.83	$814.80	$814.80