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	$69.29	6.756%	$73.9712	$73.97	$73.95	$74.00
Purchase #2	$139.70	4.247%	$145.6331	$145.63	$145.65	$145.60
Purchase #3	$163.98	13.395%	$185.9451	$185.95	$185.95	$185.90
Purchase #4	$246.29	5.523%	$259.8926	$259.89	$259.90	$259.90
Purchase #5	$8.48	12.229%	$9.517	$9.52	$9.50	$9.50
Purchase #6	$229.82	11.179%	$255.5116	$255.51	$255.50	$255.50
Purchase #7	$121.57	5.180%	$127.8673	$127.87	$127.85	$127.90
7 purchase totals =	$979.13		$1,058.3379	$1,058.34	$1,058.30	$1,058.30