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	$59.82	12.163%	$67.0959	$67.10	$67.10	$67.10
Purchase #2	$139.93	9.408%	$153.0946	$153.09	$153.10	$153.10
Purchase #3	$139.47	7.736%	$150.2594	$150.26	$150.25	$150.30
Purchase #4	$150.57	8.715%	$163.6922	$163.69	$163.70	$163.70
Purchase #5	$154.66	8.284%	$167.472	$167.47	$167.45	$167.50
Purchase #6	$216.25	6.740%	$230.8253	$230.83	$230.85	$230.80
Purchase #7	$189.82	3.722%	$196.8851	$196.89	$196.90	$196.90
7 purchase totals =	$1,050.52		$1,129.3245	$1,129.33	$1,129.35	$1,129.40