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	$191.82	11.310%	$213.5148	$213.51	$213.50	$213.50
Purchase #2	$169.38	12.338%	$190.2781	$190.28	$190.30	$190.30
Purchase #3	$208.34	5.296%	$219.3737	$219.37	$219.35	$219.40
Purchase #4	$176.52	4.849%	$185.0795	$185.08	$185.10	$185.10
Purchase #5	$20.38	13.426%	$23.1162	$23.12	$23.10	$23.10
Purchase #6	$142.56	13.622%	$161.9795	$161.98	$162.00	$162.00
Purchase #7	$187.78	6.501%	$199.9876	$199.99	$200.00	$200.00
7 purchase totals =	$1,096.78		$1,193.3294	$1,193.33	$1,193.35	$1,193.40