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	$205.71	12.429%	$231.2777	$231.28	$231.30	$231.30
Purchase #2	$217.74	5.830%	$230.4342	$230.43	$230.45	$230.40
Purchase #3	$191.76	3.319%	$198.1245	$198.12	$198.10	$198.10
Purchase #4	$96.92	3.191%	$100.0127	$100.01	$100.00	$100.00
Purchase #5	$150.34	10.151%	$165.601	$165.60	$165.60	$165.60
Purchase #6	$37.33	7.192%	$40.0148	$40.01	$40.00	$40.00
Purchase #7	$87.70	7.754%	$94.5003	$94.50	$94.50	$94.50
7 purchase totals =	$987.50		$1,059.9652	$1,059.95	$1,059.95	$1,059.90