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	$178.32	7.305%	$191.3463	$191.35	$191.35	$191.30
Purchase #2	$172.32	7.542%	$185.3164	$185.32	$185.30	$185.30
Purchase #3	$89.93	10.278%	$99.173	$99.17	$99.15	$99.20
Purchase #4	$166.79	13.321%	$189.0081	$189.01	$189.00	$189.00
Purchase #5	$103.72	5.542%	$109.4682	$109.47	$109.45	$109.50
Purchase #6	$124.58	11.737%	$139.202	$139.20	$139.20	$139.20
Purchase #7	$34.28	8.519%	$37.2003	$37.20	$37.20	$37.20
7 purchase totals =	$869.94		$950.7143	$950.72	$950.65	$950.70