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	$85.99	10.245%	$94.7997	$94.80	$94.80	$94.80
Purchase #2	$151.32	4.506%	$158.1385	$158.14	$158.15	$158.10
Purchase #3	$17.57	10.197%	$19.3616	$19.36	$19.35	$19.40
Purchase #4	$59.80	7.804%	$64.4668	$64.47	$64.45	$64.50
Purchase #5	$96.54	6.515%	$102.8296	$102.83	$102.85	$102.80
Purchase #6	$182.73	3.596%	$189.301	$189.30	$189.30	$189.30
Purchase #7	$104.50	6.542%	$111.3364	$111.34	$111.35	$111.30
7 purchase totals =	$698.45		$740.2336	$740.24	$740.25	$740.20