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	$186.98	7.230%	$200.4987	$200.50	$200.50	$200.50
Purchase #2	$166.80	5.841%	$176.5428	$176.54	$176.55	$176.50
Purchase #3	$209.50	9.310%	$229.0045	$229.00	$229.00	$229.00
Purchase #4	$33.67	5.439%	$35.5013	$35.50	$35.50	$35.50
Purchase #5	$170.38	4.821%	$178.594	$178.59	$178.60	$178.60
Purchase #6	$43.67	7.290%	$46.8535	$46.85	$46.85	$46.90
Purchase #7	$194.47	11.776%	$217.3708	$217.37	$217.35	$217.40
7 purchase totals =	$1,005.47		$1,084.3656	$1,084.35	$1,084.35	$1,084.40