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	$5.32	5.715%	$5.624	$5.62	$5.60	$5.60
Purchase #2	$28.41	8.621%	$30.8592	$30.86	$30.85	$30.90
Purchase #3	$27.55	4.409%	$28.7647	$28.76	$28.75	$28.80
Purchase #4	$38.41	10.111%	$42.2936	$42.29	$42.30	$42.30
Purchase #5	$82.47	12.212%	$92.5412	$92.54	$92.55	$92.50
Purchase #6	$136.84	6.330%	$145.502	$145.50	$145.50	$145.50
Purchase #7	$27.74	13.107%	$31.3759	$31.38	$31.40	$31.40
7 purchase totals =	$346.74		$376.9606	$376.95	$376.95	$377.00