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	$131.31	5.812%	$138.9417	$138.94	$138.95	$138.90
Purchase #2	$11.97	4.622%	$12.5233	$12.52	$12.50	$12.50
Purchase #3	$240.53	13.462%	$272.9101	$272.91	$272.90	$272.90
Purchase #4	$59.78	5.791%	$63.2419	$63.24	$63.25	$63.20
Purchase #5	$231.59	13.178%	$262.1089	$262.11	$262.10	$262.10
Purchase #6	$213.47	5.814%	$225.8811	$225.88	$225.90	$225.90
Purchase #7	$159.61	4.302%	$166.4764	$166.48	$166.50	$166.50
7 purchase totals =	$1,048.26		$1,142.0834	$1,142.08	$1,142.10	$1,142.00