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	$108.41	8.502%	$117.627	$117.63	$117.65	$117.60
Purchase #2	$156.31	11.800%	$174.7546	$174.75	$174.75	$174.80
Purchase #3	$222.94	9.202%	$243.4549	$243.45	$243.45	$243.50
Purchase #4	$140.39	8.137%	$151.8135	$151.81	$151.80	$151.80
Purchase #5	$18.34	12.221%	$20.5813	$20.58	$20.60	$20.60
Purchase #6	$162.65	3.635%	$168.5623	$168.56	$168.55	$168.60
Purchase #7	$131.89	7.163%	$141.3373	$141.34	$141.35	$141.30
7 purchase totals =	$940.93		$1,018.1309	$1,018.12	$1,018.15	$1,018.20