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	$103.55	4.716%	$108.4334	$108.43	$108.45	$108.40
Purchase #2	$247.69	9.111%	$270.257	$270.26	$270.25	$270.30
Purchase #3	$163.47	3.268%	$168.8122	$168.81	$168.80	$168.80
Purchase #4	$128.47	8.624%	$139.5493	$139.55	$139.55	$139.50
Purchase #5	$118.53	11.298%	$131.9215	$131.92	$131.90	$131.90
Purchase #6	$131.72	8.234%	$142.5658	$142.57	$142.55	$142.60
Purchase #7	$145.46	4.844%	$152.5061	$152.51	$152.50	$152.50
7 purchase totals =	$1,038.89		$1,114.0453	$1,114.05	$1,114.00	$1,114.00