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	$38.64	10.786%	$42.8077	$42.81	$42.80	$42.80
Purchase #2	$132.65	13.523%	$150.5883	$150.59	$150.60	$150.60
Purchase #3	$5.76	3.274%	$5.9486	$5.95	$5.95	$5.90
Purchase #4	$175.96	11.156%	$195.5901	$195.59	$195.60	$195.60
Purchase #5	$154.39	4.841%	$161.864	$161.86	$161.85	$161.90
Purchase #6	$156.36	6.114%	$165.9199	$165.92	$165.90	$165.90
Purchase #7	$104.32	7.820%	$112.4778	$112.48	$112.50	$112.50
7 purchase totals =	$768.08		$835.1964	$835.20	$835.20	$835.20