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	$184.91	3.369%	$191.1396	$191.14	$191.15	$191.10
Purchase #2	$163.34	5.608%	$172.5001	$172.50	$172.50	$172.50
Purchase #3	$95.33	4.793%	$99.8992	$99.90	$99.90	$99.90
Purchase #4	$192.69	3.200%	$198.8561	$198.86	$198.85	$198.90
Purchase #5	$8.53	4.178%	$8.8864	$8.89	$8.90	$8.90
Purchase #6	$27.94	4.302%	$29.142	$29.14	$29.15	$29.10
Purchase #7	$103.68	10.415%	$114.4783	$114.48	$114.50	$114.50
7 purchase totals =	$776.42		$814.9017	$814.91	$814.95	$814.90