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	$11.25	5.361%	$11.8531	$11.85	$11.85	$11.90
Purchase #2	$189.99	3.381%	$196.4136	$196.41	$196.40	$196.40
Purchase #3	$22.54	12.442%	$25.3444	$25.34	$25.35	$25.30
Purchase #4	$227.73	12.682%	$256.6107	$256.61	$256.60	$256.60
Purchase #5	$128.33	12.438%	$144.2917	$144.29	$144.30	$144.30
Purchase #6	$150.42	6.148%	$159.6678	$159.67	$159.65	$159.70
Purchase #7	$154.78	8.667%	$168.1948	$168.19	$168.20	$168.20
7 purchase totals =	$885.04		$962.3761	$962.36	$962.35	$962.40