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	$63.40	3.407%	$65.56	$65.56	$65.55	$65.60
Purchase #2	$145.41	9.380%	$159.0495	$159.05	$159.05	$159.00
Purchase #3	$182.83	6.273%	$194.2989	$194.30	$194.30	$194.30
Purchase #4	$172.50	13.734%	$196.1912	$196.19	$196.20	$196.20
Purchase #5	$42.60	13.390%	$48.3041	$48.30	$48.30	$48.30
Purchase #6	$29.95	3.746%	$31.0719	$31.07	$31.05	$31.10
Purchase #7	$161.77	3.776%	$167.8784	$167.88	$167.90	$167.90
7 purchase totals =	$798.46		$862.3540	$862.35	$862.35	$862.40