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	$74.57	3.156%	$76.9234	$76.92	$76.90	$76.90
Purchase #2	$90.96	9.691%	$99.7749	$99.77	$99.75	$99.80
Purchase #3	$154.90	5.488%	$163.4009	$163.40	$163.40	$163.40
Purchase #4	$115.75	10.519%	$127.9257	$127.93	$127.95	$127.90
Purchase #5	$186.72	5.435%	$196.8682	$196.87	$196.85	$196.90
Purchase #6	$245.36	4.294%	$255.8958	$255.90	$255.90	$255.90
Purchase #7	$37.53	12.357%	$42.1676	$42.17	$42.15	$42.20
7 purchase totals =	$905.79		$962.9565	$962.96	$962.90	$963.00