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	$10.65	5.497%	$11.2354	$11.24	$11.25	$11.20
Purchase #2	$86.56	4.500%	$90.4552	$90.46	$90.45	$90.50
Purchase #3	$178.64	13.413%	$202.601	$202.60	$202.60	$202.60
Purchase #4	$78.53	10.272%	$86.5966	$86.60	$86.60	$86.60
Purchase #5	$219.32	3.338%	$226.6409	$226.64	$226.65	$226.60
Purchase #6	$24.89	3.757%	$25.8251	$25.83	$25.85	$25.80
Purchase #7	$138.89	10.804%	$153.8957	$153.90	$153.90	$153.90
7 purchase totals =	$737.48		$797.2499	$797.27	$797.30	$797.20