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	$183.78	13.475%	$208.5444	$208.54	$208.55	$208.50
Purchase #2	$134.79	4.152%	$140.3865	$140.39	$140.40	$140.40
Purchase #3	$157.98	4.187%	$164.5946	$164.59	$164.60	$164.60
Purchase #4	$71.50	11.165%	$79.483	$79.48	$79.50	$79.50
Purchase #5	$53.33	4.734%	$55.8546	$55.85	$55.85	$55.90
Purchase #6	$174.28	4.642%	$182.3701	$182.37	$182.35	$182.40
Purchase #7	$203.68	5.400%	$214.6787	$214.68	$214.70	$214.70
7 purchase totals =	$979.34		$1,045.9119	$1,045.90	$1,045.95	$1,046.00