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	$163.46	3.151%	$168.6106	$168.61	$168.60	$168.60
Purchase #2	$84.37	11.391%	$93.9806	$93.98	$94.00	$94.00
Purchase #3	$38.51	5.537%	$40.6423	$40.64	$40.65	$40.60
Purchase #4	$149.57	9.766%	$164.177	$164.18	$164.20	$164.20
Purchase #5	$93.93	11.166%	$104.4182	$104.42	$104.40	$104.40
Purchase #6	$137.90	4.596%	$144.2379	$144.24	$144.25	$144.20
Purchase #7	$139.44	3.477%	$144.2883	$144.29	$144.30	$144.30
7 purchase totals =	$807.18		$860.3549	$860.36	$860.40	$860.30