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	$103.47	7.715%	$111.4527	$111.45	$111.45	$111.50
Purchase #2	$228.84	10.787%	$253.525	$253.53	$253.55	$253.50
Purchase #3	$42.72	10.116%	$47.0416	$47.04	$47.05	$47.00
Purchase #4	$121.50	10.115%	$133.7897	$133.79	$133.80	$133.80
Purchase #5	$196.25	7.583%	$211.1316	$211.13	$211.15	$211.10
Purchase #6	$83.82	9.374%	$91.6773	$91.68	$91.70	$91.70
Purchase #7	$113.78	4.725%	$119.1561	$119.16	$119.15	$119.20
7 purchase totals =	$890.38		$967.7740	$967.78	$967.85	$967.80