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	$216.32	3.708%	$224.3411	$224.34	$224.35	$224.30
Purchase #2	$109.47	7.220%	$117.3737	$117.37	$117.35	$117.40
Purchase #3	$78.75	5.222%	$82.8623	$82.86	$82.85	$82.90
Purchase #4	$241.78	9.605%	$265.003	$265.00	$265.00	$265.00
Purchase #5	$160.34	13.342%	$181.7326	$181.73	$181.75	$181.70
Purchase #6	$13.77	3.469%	$14.2477	$14.25	$14.25	$14.20
Purchase #7	$56.94	4.591%	$59.5541	$59.55	$59.55	$59.60
7 purchase totals =	$877.37		$945.1145	$945.10	$945.10	$945.10