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	$25.35	4.183%	$26.4104	$26.41	$26.40	$26.40
Purchase #2	$150.71	4.513%	$157.5115	$157.51	$157.50	$157.50
Purchase #3	$98.57	10.803%	$109.2185	$109.22	$109.20	$109.20
Purchase #4	$131.89	3.495%	$136.4996	$136.50	$136.50	$136.50
Purchase #5	$144.77	13.737%	$164.6571	$164.66	$164.65	$164.70
Purchase #6	$238.87	8.465%	$259.0903	$259.09	$259.10	$259.10
Purchase #7	$209.48	6.678%	$223.4691	$223.47	$223.45	$223.50
7 purchase totals =	$999.64		$1,076.8565	$1,076.86	$1,076.80	$1,076.90