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	$199.50	8.563%	$216.5832	$216.58	$216.60	$216.60
Purchase #2	$114.86	3.849%	$119.281	$119.28	$119.30	$119.30
Purchase #3	$55.61	11.235%	$61.8578	$61.86	$61.85	$61.90
Purchase #4	$90.43	5.847%	$95.7174	$95.72	$95.70	$95.70
Purchase #5	$186.40	5.238%	$196.1636	$196.16	$196.15	$196.20
Purchase #6	$172.85	5.122%	$181.7034	$181.70	$181.70	$181.70
Purchase #7	$183.61	11.620%	$204.9455	$204.95	$204.95	$204.90
7 purchase totals =	$1,003.26		$1,076.2519	$1,076.25	$1,076.25	$1,076.30