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	$124.84	5.438%	$131.6288	$131.63	$131.65	$131.60
Purchase #2	$153.59	10.254%	$169.3391	$169.34	$169.35	$169.30
Purchase #3	$47.73	6.497%	$50.831	$50.83	$50.85	$50.80
Purchase #4	$109.28	13.260%	$123.7705	$123.77	$123.75	$123.80
Purchase #5	$76.92	11.349%	$85.6497	$85.65	$85.65	$85.60
Purchase #6	$63.83	4.323%	$66.5894	$66.59	$66.60	$66.60
Purchase #7	$78.84	12.386%	$88.6051	$88.61	$88.60	$88.60
7 purchase totals =	$655.03		$716.4136	$716.42	$716.45	$716.30