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	$67.55	6.332%	$71.8273	$71.83	$71.85	$71.80
Purchase #2	$43.25	9.801%	$47.4889	$47.49	$47.50	$47.50
Purchase #3	$181.44	11.809%	$202.8662	$202.87	$202.85	$202.90
Purchase #4	$107.94	10.351%	$119.1129	$119.11	$119.10	$119.10
Purchase #5	$64.80	10.627%	$71.6863	$71.69	$71.70	$71.70
Purchase #6	$100.95	10.216%	$111.2631	$111.26	$111.25	$111.30
Purchase #7	$164.73	5.387%	$173.604	$173.60	$173.60	$173.60
7 purchase totals =	$730.66		$797.8487	$797.85	$797.85	$797.90