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	$130.92	11.167%	$145.5398	$145.54	$145.55	$145.50
Purchase #2	$217.73	6.866%	$232.6793	$232.68	$232.70	$232.70
Purchase #3	$213.51	4.243%	$222.5692	$222.57	$222.55	$222.60
Purchase #4	$162.60	4.280%	$169.5593	$169.56	$169.55	$169.60
Purchase #5	$45.83	12.452%	$51.5368	$51.54	$51.55	$51.50
Purchase #6	$150.47	4.320%	$156.9703	$156.97	$156.95	$157.00
Purchase #7	$169.82	5.659%	$179.4301	$179.43	$179.45	$179.40
7 purchase totals =	$1,090.88		$1,158.2848	$1,158.29	$1,158.30	$1,158.30