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	$216.31	5.814%	$228.8863	$228.89	$228.90	$228.90
Purchase #2	$96.80	4.439%	$101.097	$101.10	$101.10	$101.10
Purchase #3	$35.51	3.771%	$36.8491	$36.85	$36.85	$36.80
Purchase #4	$214.90	7.134%	$230.231	$230.23	$230.25	$230.20
Purchase #5	$117.89	11.621%	$131.59	$131.59	$131.60	$131.60
Purchase #6	$222.72	5.179%	$234.2547	$234.25	$234.25	$234.30
Purchase #7	$31.55	10.748%	$34.941	$34.94	$34.95	$34.90
7 purchase totals =	$935.68		$997.8491	$997.85	$997.90	$997.80