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	$119.72	12.168%	$134.2875	$134.29	$134.30	$134.30
Purchase #2	$105.58	12.836%	$119.1322	$119.13	$119.15	$119.10
Purchase #3	$230.92	7.746%	$248.8071	$248.81	$248.80	$248.80
Purchase #4	$91.36	9.253%	$99.8135	$99.81	$99.80	$99.80
Purchase #5	$146.65	9.509%	$160.5949	$160.59	$160.60	$160.60
Purchase #6	$78.66	12.777%	$88.7104	$88.71	$88.70	$88.70
Purchase #7	$168.93	10.790%	$187.1575	$187.16	$187.15	$187.20
7 purchase totals =	$941.82		$1,038.5031	$1,038.50	$1,038.50	$1,038.50