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	$203.52	4.649%	$212.9816	$212.98	$213.00	$213.00
Purchase #2	$159.67	12.552%	$179.7118	$179.71	$179.70	$179.70
Purchase #3	$101.55	10.232%	$111.9406	$111.94	$111.95	$111.90
Purchase #4	$152.38	8.696%	$165.631	$165.63	$165.65	$165.60
Purchase #5	$58.39	10.411%	$64.469	$64.47	$64.45	$64.50
Purchase #6	$72.99	5.234%	$76.8103	$76.81	$76.80	$76.80
Purchase #7	$231.50	13.116%	$261.8635	$261.86	$261.85	$261.90
7 purchase totals =	$980.00		$1,073.4078	$1,073.40	$1,073.40	$1,073.40