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	$51.73	3.622%	$53.6037	$53.60	$53.60	$53.60
Purchase #2	$220.91	5.696%	$233.493	$233.49	$233.50	$233.50
Purchase #3	$205.85	9.735%	$225.8895	$225.89	$225.90	$225.90
Purchase #4	$37.61	9.276%	$41.0987	$41.10	$41.10	$41.10
Purchase #5	$223.41	13.219%	$252.9426	$252.94	$252.95	$252.90
Purchase #6	$124.67	13.274%	$141.2187	$141.22	$141.20	$141.20
Purchase #7	$65.90	11.587%	$73.5358	$73.54	$73.55	$73.50
7 purchase totals =	$930.08		$1,021.7820	$1,021.78	$1,021.80	$1,021.70