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	$240.86	9.464%	$263.655	$263.66	$263.65	$263.70
Purchase #2	$175.77	6.221%	$186.7047	$186.70	$186.70	$186.70
Purchase #3	$27.43	8.343%	$29.7185	$29.72	$29.70	$29.70
Purchase #4	$62.81	13.772%	$71.4602	$71.46	$71.45	$71.50
Purchase #5	$52.79	12.728%	$59.5091	$59.51	$59.50	$59.50
Purchase #6	$5.48	5.171%	$5.7634	$5.76	$5.75	$5.80
Purchase #7	$156.50	7.131%	$167.66	$167.66	$167.65	$167.70
7 purchase totals =	$721.64		$784.4709	$784.47	$784.40	$784.60