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	$30.34	8.559%	$32.9368	$32.94	$32.95	$32.90
Purchase #2	$147.86	7.233%	$158.5547	$158.55	$158.55	$158.60
Purchase #3	$242.36	7.758%	$261.1623	$261.16	$261.15	$261.20
Purchase #4	$123.87	9.870%	$136.096	$136.10	$136.10	$136.10
Purchase #5	$157.69	13.863%	$179.5506	$179.55	$179.55	$179.60
Purchase #6	$219.57	4.223%	$228.8424	$228.84	$228.85	$228.80
Purchase #7	$43.74	4.806%	$45.8421	$45.84	$45.85	$45.80
7 purchase totals =	$965.43		$1,042.9849	$1,042.98	$1,043.00	$1,043.00