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	$214.66	5.342%	$226.1271	$226.13	$226.15	$226.10
Purchase #2	$104.30	9.182%	$113.8768	$113.88	$113.90	$113.90
Purchase #3	$157.25	9.796%	$172.6542	$172.65	$172.65	$172.70
Purchase #4	$141.36	6.689%	$150.8156	$150.82	$150.80	$150.80
Purchase #5	$135.41	13.746%	$154.0235	$154.02	$154.00	$154.00
Purchase #6	$100.45	7.794%	$108.2791	$108.28	$108.30	$108.30
Purchase #7	$119.46	10.381%	$131.8611	$131.86	$131.85	$131.90
7 purchase totals =	$972.89		$1,057.6374	$1,057.64	$1,057.65	$1,057.70