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	$118.80	13.473%	$134.8059	$134.81	$134.80	$134.80
Purchase #2	$238.73	13.347%	$270.5933	$270.59	$270.60	$270.60
Purchase #3	$124.82	5.445%	$131.6164	$131.62	$131.60	$131.60
Purchase #4	$91.86	9.678%	$100.7502	$100.75	$100.75	$100.80
Purchase #5	$94.58	4.122%	$98.4786	$98.48	$98.50	$98.50
Purchase #6	$97.40	12.441%	$109.5175	$109.52	$109.50	$109.50
Purchase #7	$148.73	10.214%	$163.9213	$163.92	$163.90	$163.90
7 purchase totals =	$914.92		$1,009.6832	$1,009.69	$1,009.65	$1,009.70