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	$167.39	9.333%	$183.0125	$183.01	$183.00	$183.00
Purchase #2	$186.78	11.268%	$207.8264	$207.83	$207.85	$207.80
Purchase #3	$78.48	10.259%	$86.5313	$86.53	$86.55	$86.50
Purchase #4	$233.25	9.487%	$255.3784	$255.38	$255.40	$255.40
Purchase #5	$21.70	5.554%	$22.9052	$22.91	$22.90	$22.90
Purchase #6	$196.57	10.249%	$216.7165	$216.72	$216.70	$216.70
Purchase #7	$54.85	9.301%	$59.9516	$59.95	$59.95	$60.00
7 purchase totals =	$939.02		$1,032.3219	$1,032.33	$1,032.35	$1,032.30