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	$137.89	5.568%	$145.5677	$145.57	$145.55	$145.60
Purchase #2	$142.55	6.644%	$152.021	$152.02	$152.00	$152.00
Purchase #3	$120.78	13.745%	$137.3812	$137.38	$137.40	$137.40
Purchase #4	$166.59	3.433%	$172.309	$172.31	$172.30	$172.30
Purchase #5	$150.82	5.361%	$158.9055	$158.91	$158.90	$158.90
Purchase #6	$187.25	12.615%	$210.8716	$210.87	$210.85	$210.90
Purchase #7	$216.56	12.785%	$244.2472	$244.25	$244.25	$244.20
7 purchase totals =	$1,122.44		$1,221.3032	$1,221.31	$1,221.25	$1,221.30