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	$141.71	6.384%	$150.7568	$150.76	$150.75	$150.80
Purchase #2	$27.94	12.268%	$31.3677	$31.37	$31.35	$31.40
Purchase #3	$231.46	12.289%	$259.9041	$259.90	$259.90	$259.90
Purchase #4	$165.49	9.305%	$180.8888	$180.89	$180.90	$180.90
Purchase #5	$161.43	4.672%	$168.972	$168.97	$168.95	$169.00
Purchase #6	$145.89	9.465%	$159.6985	$159.70	$159.70	$159.70
Purchase #7	$11.40	8.294%	$12.3455	$12.35	$12.35	$12.30
7 purchase totals =	$885.32		$963.9334	$963.94	$963.90	$964.00