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	$83.71	12.723%	$94.3604	$94.36	$94.35	$94.40
Purchase #2	$92.78	11.569%	$103.5137	$103.51	$103.50	$103.50
Purchase #3	$168.78	11.120%	$187.5483	$187.55	$187.55	$187.50
Purchase #4	$105.82	5.784%	$111.9406	$111.94	$111.95	$111.90
Purchase #5	$96.32	3.176%	$99.3791	$99.38	$99.40	$99.40
Purchase #6	$80.26	4.522%	$83.8894	$83.89	$83.90	$83.90
Purchase #7	$82.66	5.158%	$86.9236	$86.92	$86.90	$86.90
7 purchase totals =	$710.33		$767.5551	$767.55	$767.55	$767.50