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	$130.73	7.395%	$140.3975	$140.40	$140.40	$140.40
Purchase #2	$112.38	11.744%	$125.5779	$125.58	$125.60	$125.60
Purchase #3	$16.83	5.434%	$17.7445	$17.74	$17.75	$17.70
Purchase #4	$59.38	9.504%	$65.0235	$65.02	$65.00	$65.00
Purchase #5	$102.27	8.611%	$111.0765	$111.08	$111.10	$111.10
Purchase #6	$82.90	7.767%	$89.3388	$89.34	$89.35	$89.30
Purchase #7	$150.96	4.835%	$158.2589	$158.26	$158.25	$158.30
7 purchase totals =	$655.45		$707.4176	$707.42	$707.45	$707.40