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	$29.41	13.853%	$33.4842	$33.48	$33.50	$33.50
Purchase #2	$88.38	11.511%	$98.5534	$98.55	$98.55	$98.60
Purchase #3	$190.85	10.181%	$210.2804	$210.28	$210.30	$210.30
Purchase #4	$212.89	5.463%	$224.5202	$224.52	$224.50	$224.50
Purchase #5	$114.41	8.387%	$124.0056	$124.01	$124.00	$124.00
Purchase #6	$121.88	7.356%	$130.8455	$130.85	$130.85	$130.80
Purchase #7	$225.66	12.258%	$253.3214	$253.32	$253.30	$253.30
7 purchase totals =	$983.48		$1,075.0107	$1,075.01	$1,075.00	$1,075.00