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	$217.58	8.770%	$236.6618	$236.66	$236.65	$236.70
Purchase #2	$198.89	6.240%	$211.3007	$211.30	$211.30	$211.30
Purchase #3	$78.76	13.633%	$89.4974	$89.50	$89.50	$89.50
Purchase #4	$216.47	11.151%	$240.6086	$240.61	$240.60	$240.60
Purchase #5	$215.48	7.116%	$230.8136	$230.81	$230.80	$230.80
Purchase #6	$219.53	3.478%	$227.1653	$227.17	$227.15	$227.20
Purchase #7	$84.95	5.129%	$89.3071	$89.31	$89.30	$89.30
7 purchase totals =	$1,231.66		$1,325.3545	$1,325.36	$1,325.30	$1,325.40