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	$209.37	10.379%	$231.1005	$231.10	$231.10	$231.10
Purchase #2	$213.45	9.787%	$234.3404	$234.34	$234.35	$234.30
Purchase #3	$40.98	10.544%	$45.3009	$45.30	$45.30	$45.30
Purchase #4	$181.92	4.820%	$190.6885	$190.69	$190.70	$190.70
Purchase #5	$211.72	5.574%	$223.5213	$223.52	$223.50	$223.50
Purchase #6	$100.94	7.495%	$108.5055	$108.51	$108.50	$108.50
Purchase #7	$164.51	6.246%	$174.7853	$174.79	$174.80	$174.80
7 purchase totals =	$1,122.89		$1,208.2424	$1,208.25	$1,208.25	$1,208.20