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	$103.71	13.347%	$117.5522	$117.55	$117.55	$117.60
Purchase #2	$156.41	11.851%	$174.9461	$174.95	$174.95	$174.90
Purchase #3	$241.56	4.173%	$251.6403	$251.64	$251.65	$251.60
Purchase #4	$131.25	10.370%	$144.8606	$144.86	$144.85	$144.90
Purchase #5	$74.85	4.684%	$78.356	$78.36	$78.35	$78.40
Purchase #6	$140.92	6.538%	$150.1333	$150.13	$150.15	$150.10
Purchase #7	$34.75	4.649%	$36.3655	$36.37	$36.35	$36.40
7 purchase totals =	$883.45		$953.8540	$953.86	$953.85	$953.90