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	$62.38	8.790%	$67.8632	$67.86	$67.85	$67.90
Purchase #2	$158.35	10.207%	$174.5128	$174.51	$174.50	$174.50
Purchase #3	$33.66	3.292%	$34.7681	$34.77	$34.75	$34.80
Purchase #4	$153.36	11.659%	$171.2402	$171.24	$171.25	$171.20
Purchase #5	$153.96	6.179%	$163.4732	$163.47	$163.45	$163.50
Purchase #6	$53.69	10.584%	$59.3725	$59.37	$59.35	$59.40
Purchase #7	$68.65	3.792%	$71.2532	$71.25	$71.25	$71.30
7 purchase totals =	$684.05		$742.4832	$742.47	$742.40	$742.60