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	$87.69	9.649%	$96.1512	$96.15	$96.15	$96.20
Purchase #2	$142.62	5.433%	$150.3685	$150.37	$150.35	$150.40
Purchase #3	$169.62	13.468%	$192.4644	$192.46	$192.45	$192.50
Purchase #4	$210.38	10.172%	$231.7799	$231.78	$231.80	$231.80
Purchase #5	$143.43	10.464%	$158.4385	$158.44	$158.45	$158.40
Purchase #6	$91.42	12.630%	$102.9663	$102.97	$102.95	$103.00
Purchase #7	$64.70	10.270%	$71.3447	$71.34	$71.35	$71.30
7 purchase totals =	$909.86		$1,003.5135	$1,003.51	$1,003.50	$1,003.60