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	$230.40	11.349%	$256.5481	$256.55	$256.55	$256.50
Purchase #2	$194.58	13.698%	$221.2336	$221.23	$221.25	$221.20
Purchase #3	$122.85	11.808%	$137.3561	$137.36	$137.35	$137.40
Purchase #4	$69.81	12.348%	$78.4301	$78.43	$78.45	$78.40
Purchase #5	$93.95	4.347%	$98.034	$98.03	$98.05	$98.00
Purchase #6	$106.45	3.248%	$109.9075	$109.91	$109.90	$109.90
Purchase #7	$59.51	12.115%	$66.7196	$66.72	$66.70	$66.70
7 purchase totals =	$877.55		$968.2290	$968.23	$968.25	$968.10