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	$197.35	12.502%	$222.0227	$222.02	$222.00	$222.00
Purchase #2	$165.56	11.790%	$185.0795	$185.08	$185.10	$185.10
Purchase #3	$46.37	11.854%	$51.8667	$51.87	$51.85	$51.90
Purchase #4	$76.87	12.305%	$86.3289	$86.33	$86.35	$86.30
Purchase #5	$204.80	5.177%	$215.4025	$215.40	$215.40	$215.40
Purchase #6	$157.87	4.478%	$164.9394	$164.94	$164.95	$164.90
Purchase #7	$119.45	10.284%	$131.7342	$131.73	$131.75	$131.70
7 purchase totals =	$968.27		$1,057.3739	$1,057.37	$1,057.40	$1,057.30