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	$9.63	11.562%	$10.7434	$10.74	$10.75	$10.70
Purchase #2	$26.72	9.424%	$29.2381	$29.24	$29.25	$29.20
Purchase #3	$37.69	3.305%	$38.9357	$38.94	$38.95	$38.90
Purchase #4	$56.71	4.854%	$59.4627	$59.46	$59.45	$59.50
Purchase #5	$31.82	10.486%	$35.1566	$35.16	$35.15	$35.20
Purchase #6	$128.84	13.226%	$145.8804	$145.88	$145.90	$145.90
Purchase #7	$111.70	8.216%	$120.8773	$120.88	$120.90	$120.90
7 purchase totals =	$403.11		$440.2942	$440.30	$440.35	$440.30