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	$98.46	13.343%	$111.5975	$111.60	$111.60	$111.60
Purchase #2	$10.77	10.665%	$11.9186	$11.92	$11.90	$11.90
Purchase #3	$79.38	3.112%	$81.8503	$81.85	$81.85	$81.90
Purchase #4	$216.57	3.549%	$224.2561	$224.26	$224.25	$224.30
Purchase #5	$151.31	3.438%	$156.512	$156.51	$156.50	$156.50
Purchase #6	$179.89	7.831%	$193.9772	$193.98	$194.00	$194.00
Purchase #7	$50.31	9.504%	$55.0915	$55.09	$55.10	$55.10
7 purchase totals =	$786.69		$835.2032	$835.21	$835.20	$835.30