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	$117.81	11.700%	$131.5938	$131.59	$131.60	$131.60
Purchase #2	$40.32	4.247%	$42.0324	$42.03	$42.05	$42.00
Purchase #3	$52.97	11.299%	$58.9551	$58.96	$58.95	$59.00
Purchase #4	$213.92	7.314%	$229.5661	$229.57	$229.55	$229.60
Purchase #5	$69.53	12.868%	$78.4771	$78.48	$78.50	$78.50
Purchase #6	$99.86	4.308%	$104.162	$104.16	$104.15	$104.20
Purchase #7	$61.42	12.809%	$69.2873	$69.29	$69.30	$69.30
7 purchase totals =	$655.83		$714.0738	$714.08	$714.10	$714.20