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	$37.33	8.342%	$40.4441	$40.44	$40.45	$40.40
Purchase #2	$53.49	12.220%	$60.0265	$60.03	$60.05	$60.00
Purchase #3	$105.83	5.394%	$111.5385	$111.54	$111.55	$111.50
Purchase #4	$171.46	8.576%	$186.1644	$186.16	$186.15	$186.20
Purchase #5	$14.43	5.556%	$15.2317	$15.23	$15.25	$15.20
Purchase #6	$121.84	8.288%	$131.9381	$131.94	$131.95	$131.90
Purchase #7	$161.86	4.332%	$168.8718	$168.87	$168.85	$168.90
7 purchase totals =	$666.24		$714.2151	$714.21	$714.25	$714.10