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	$186.43	13.229%	$211.0928	$211.09	$211.10	$211.10
Purchase #2	$39.51	4.708%	$41.3701	$41.37	$41.35	$41.40
Purchase #3	$223.83	3.282%	$231.1761	$231.18	$231.20	$231.20
Purchase #4	$76.35	13.202%	$86.4297	$86.43	$86.45	$86.40
Purchase #5	$69.56	3.869%	$72.2513	$72.25	$72.25	$72.30
Purchase #6	$78.77	3.831%	$81.7877	$81.79	$81.80	$81.80
Purchase #7	$173.79	3.407%	$179.711	$179.71	$179.70	$179.70
7 purchase totals =	$848.24		$903.8187	$903.82	$903.85	$903.90