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	$92.95	11.707%	$103.8317	$103.83	$103.85	$103.80
Purchase #2	$187.29	3.606%	$194.0437	$194.04	$194.05	$194.00
Purchase #3	$52.92	11.516%	$59.0143	$59.01	$59.00	$59.00
Purchase #4	$27.82	7.305%	$29.8523	$29.85	$29.85	$29.90
Purchase #5	$177.69	8.227%	$192.3086	$192.31	$192.30	$192.30
Purchase #6	$31.69	12.741%	$35.7276	$35.73	$35.75	$35.70
Purchase #7	$128.65	4.406%	$134.3183	$134.32	$134.30	$134.30
7 purchase totals =	$699.01		$749.0965	$749.09	$749.10	$749.00