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	$196.76	12.836%	$222.0161	$222.02	$222.00	$222.00
Purchase #2	$112.54	9.742%	$123.5036	$123.50	$123.50	$123.50
Purchase #3	$31.53	7.242%	$33.8134	$33.81	$33.80	$33.80
Purchase #4	$40.64	3.532%	$42.0754	$42.08	$42.10	$42.10
Purchase #5	$34.90	13.226%	$39.5159	$39.52	$39.50	$39.50
Purchase #6	$17.67	11.679%	$19.7337	$19.73	$19.75	$19.70
Purchase #7	$31.74	8.603%	$34.4706	$34.47	$34.45	$34.50
7 purchase totals =	$465.78		$515.1287	$515.13	$515.10	$515.10