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	$70.29	4.107%	$73.1768	$73.18	$73.20	$73.20
Purchase #2	$11.70	7.777%	$12.6099	$12.61	$12.60	$12.60
Purchase #3	$141.36	7.779%	$152.3564	$152.36	$152.35	$152.40
Purchase #4	$28.77	12.858%	$32.4692	$32.47	$32.45	$32.50
Purchase #5	$78.86	9.783%	$86.5749	$86.57	$86.55	$86.60
Purchase #6	$35.65	9.116%	$38.8999	$38.90	$38.90	$38.90
Purchase #7	$48.37	13.611%	$54.9536	$54.95	$54.95	$55.00
7 purchase totals =	$415.00		$451.0407	$451.04	$451.00	$451.20