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	$163.78	5.606%	$172.9615	$172.96	$172.95	$173.00
Purchase #2	$13.45	6.483%	$14.322	$14.32	$14.30	$14.30
Purchase #3	$129.57	9.767%	$142.2251	$142.23	$142.25	$142.20
Purchase #4	$162.43	11.179%	$180.588	$180.59	$180.60	$180.60
Purchase #5	$36.72	9.354%	$40.1548	$40.15	$40.15	$40.20
Purchase #6	$171.39	13.291%	$194.1694	$194.17	$194.15	$194.20
Purchase #7	$81.51	13.833%	$92.7853	$92.79	$92.80	$92.80
7 purchase totals =	$758.85		$837.2061	$837.21	$837.20	$837.30