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	$101.69	7.297%	$109.1103	$109.11	$109.10	$109.10
Purchase #2	$152.98	13.131%	$173.0678	$173.07	$173.05	$173.10
Purchase #3	$241.71	6.578%	$257.6097	$257.61	$257.60	$257.60
Purchase #4	$47.96	8.615%	$52.0918	$52.09	$52.10	$52.10
Purchase #5	$34.53	8.834%	$37.5804	$37.58	$37.60	$37.60
Purchase #6	$174.28	9.215%	$190.3399	$190.34	$190.35	$190.30
Purchase #7	$236.63	10.414%	$261.2726	$261.27	$261.25	$261.30
7 purchase totals =	$989.78		$1,081.0725	$1,081.07	$1,081.05	$1,081.10