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	$178.73	11.856%	$199.9202	$199.92	$199.90	$199.90
Purchase #2	$95.39	5.186%	$100.3369	$100.34	$100.35	$100.30
Purchase #3	$34.96	6.491%	$37.2293	$37.23	$37.25	$37.20
Purchase #4	$232.97	11.496%	$259.7522	$259.75	$259.75	$259.80
Purchase #5	$75.25	5.664%	$79.5122	$79.51	$79.50	$79.50
Purchase #6	$92.48	12.636%	$104.1658	$104.17	$104.15	$104.20
Purchase #7	$131.75	7.798%	$142.0239	$142.02	$142.00	$142.00
7 purchase totals =	$841.53		$922.9405	$922.94	$922.90	$922.90