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	$205.74	8.358%	$222.9357	$222.94	$222.95	$222.90
Purchase #2	$67.34	12.322%	$75.6376	$75.64	$75.65	$75.60
Purchase #3	$131.85	10.224%	$145.3303	$145.33	$145.35	$145.30
Purchase #4	$171.68	3.582%	$177.8296	$177.83	$177.85	$177.80
Purchase #5	$159.42	8.272%	$172.6072	$172.61	$172.60	$172.60
Purchase #6	$185.33	6.555%	$197.4784	$197.48	$197.50	$197.50
Purchase #7	$62.89	10.382%	$69.4192	$69.42	$69.40	$69.40
7 purchase totals =	$984.25		$1,061.2380	$1,061.25	$1,061.30	$1,061.10