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	$174.46	9.430%	$190.9116	$190.91	$190.90	$190.90
Purchase #2	$136.81	3.214%	$141.2071	$141.21	$141.20	$141.20
Purchase #3	$61.57	10.173%	$67.8335	$67.83	$67.85	$67.80
Purchase #4	$49.73	3.771%	$51.6053	$51.61	$51.60	$51.60
Purchase #5	$90.58	3.713%	$93.9432	$93.94	$93.95	$93.90
Purchase #6	$117.35	12.149%	$131.6069	$131.61	$131.60	$131.60
Purchase #7	$32.95	8.164%	$35.64	$35.64	$35.65	$35.60
7 purchase totals =	$663.45		$712.7476	$712.75	$712.75	$712.60