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	$65.62	10.619%	$72.5882	$72.59	$72.60	$72.60
Purchase #2	$52.29	5.614%	$55.2256	$55.23	$55.25	$55.20
Purchase #3	$102.45	11.230%	$113.9551	$113.96	$113.95	$114.00
Purchase #4	$166.78	11.126%	$185.3359	$185.34	$185.35	$185.30
Purchase #5	$78.96	9.587%	$86.5299	$86.53	$86.55	$86.50
Purchase #6	$6.43	9.461%	$7.0383	$7.04	$7.05	$7.00
Purchase #7	$98.43	11.693%	$109.9394	$109.94	$109.95	$109.90
7 purchase totals =	$570.96		$630.6124	$630.63	$630.70	$630.50