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	$83.43	12.633%	$93.9697	$93.97	$93.95	$94.00
Purchase #2	$178.40	4.104%	$185.7215	$185.72	$185.70	$185.70
Purchase #3	$50.37	8.384%	$54.593	$54.59	$54.60	$54.60
Purchase #4	$100.64	12.379%	$113.0982	$113.10	$113.10	$113.10
Purchase #5	$10.90	11.481%	$12.1514	$12.15	$12.15	$12.20
Purchase #6	$89.33	3.870%	$92.7871	$92.79	$92.80	$92.80
Purchase #7	$57.89	12.463%	$65.1048	$65.10	$65.10	$65.10
7 purchase totals =	$570.96		$617.4257	$617.42	$617.40	$617.50