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	$41.32	8.767%	$44.9425	$44.94	$44.95	$44.90
Purchase #2	$112.78	11.849%	$126.1433	$126.14	$126.15	$126.10
Purchase #3	$180.62	3.264%	$186.5154	$186.52	$186.50	$186.50
Purchase #4	$126.40	11.397%	$140.8058	$140.81	$140.80	$140.80
Purchase #5	$70.26	3.345%	$72.6102	$72.61	$72.60	$72.60
Purchase #6	$180.87	8.491%	$196.2277	$196.23	$196.25	$196.20
Purchase #7	$213.71	9.124%	$233.2089	$233.21	$233.20	$233.20
7 purchase totals =	$925.96		$1,000.4538	$1,000.46	$1,000.45	$1,000.30