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	$141.35	5.799%	$149.5469	$149.55	$149.55	$149.50
Purchase #2	$105.52	4.728%	$110.509	$110.51	$110.50	$110.50
Purchase #3	$76.53	9.118%	$83.508	$83.51	$83.50	$83.50
Purchase #4	$122.42	11.404%	$136.3808	$136.38	$136.40	$136.40
Purchase #5	$68.95	5.757%	$72.9195	$72.92	$72.90	$72.90
Purchase #6	$154.57	9.261%	$168.8847	$168.88	$168.90	$168.90
Purchase #7	$215.90	4.554%	$225.7321	$225.73	$225.75	$225.70
7 purchase totals =	$885.24		$947.4810	$947.48	$947.50	$947.40