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	$31.92	7.178%	$34.2112	$34.21	$34.20	$34.20
Purchase #2	$119.57	6.543%	$127.3935	$127.39	$127.40	$127.40
Purchase #3	$248.79	6.501%	$264.9638	$264.96	$264.95	$265.00
Purchase #4	$17.54	11.228%	$19.5094	$19.51	$19.50	$19.50
Purchase #5	$20.39	5.225%	$21.4554	$21.46	$21.45	$21.50
Purchase #6	$240.39	4.605%	$251.46	$251.46	$251.45	$251.50
Purchase #7	$201.56	7.172%	$216.0159	$216.02	$216.00	$216.00
7 purchase totals =	$880.16		$935.0092	$935.01	$934.95	$935.10