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	$145.43	6.224%	$154.4816	$154.48	$154.50	$154.50
Purchase #2	$98.86	6.252%	$105.0407	$105.04	$105.05	$105.00
Purchase #3	$52.96	5.208%	$55.7182	$55.72	$55.70	$55.70
Purchase #4	$36.73	12.712%	$41.3991	$41.40	$41.40	$41.40
Purchase #5	$94.74	10.753%	$104.9274	$104.93	$104.95	$104.90
Purchase #6	$86.82	13.580%	$98.6102	$98.61	$98.60	$98.60
Purchase #7	$122.29	7.801%	$131.8298	$131.83	$131.85	$131.80
7 purchase totals =	$637.83		$692.0070	$692.01	$692.05	$691.90