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	$35.89	8.109%	$38.8003	$38.80	$38.80	$38.80
Purchase #2	$35.98	12.555%	$40.4973	$40.50	$40.50	$40.50
Purchase #3	$65.53	6.703%	$69.9225	$69.92	$69.90	$69.90
Purchase #4	$182.87	4.730%	$191.5198	$191.52	$191.50	$191.50
Purchase #5	$104.94	5.559%	$110.7736	$110.77	$110.75	$110.80
Purchase #6	$180.98	10.591%	$200.1476	$200.15	$200.15	$200.10
Purchase #7	$47.46	7.195%	$50.8747	$50.87	$50.85	$50.90
7 purchase totals =	$653.65		$702.5358	$702.53	$702.45	$702.50