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	$201.46	10.141%	$221.8901	$221.89	$221.90	$221.90
Purchase #2	$164.57	3.606%	$170.5044	$170.50	$170.50	$170.50
Purchase #3	$214.87	6.270%	$228.3423	$228.34	$228.35	$228.30
Purchase #4	$52.86	8.564%	$57.3869	$57.39	$57.40	$57.40
Purchase #5	$65.69	9.855%	$72.1637	$72.16	$72.15	$72.20
Purchase #6	$89.81	12.279%	$100.8378	$100.84	$100.85	$100.80
Purchase #7	$115.43	3.467%	$119.432	$119.43	$119.45	$119.40
7 purchase totals =	$904.69		$970.5572	$970.55	$970.60	$970.50