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	$94.49	4.186%	$98.4454	$98.45	$98.45	$98.40
Purchase #2	$232.28	9.691%	$254.7903	$254.79	$254.80	$254.80
Purchase #3	$225.67	3.849%	$234.356	$234.36	$234.35	$234.40
Purchase #4	$21.40	6.672%	$22.8278	$22.83	$22.85	$22.80
Purchase #5	$123.95	6.211%	$131.6485	$131.65	$131.65	$131.60
Purchase #6	$90.88	9.253%	$99.2891	$99.29	$99.30	$99.30
Purchase #7	$216.31	8.106%	$233.8441	$233.84	$233.85	$233.80
7 purchase totals =	$1,004.98		$1,075.2012	$1,075.21	$1,075.25	$1,075.10