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	$36.49	10.801%	$40.4313	$40.43	$40.45	$40.40
Purchase #2	$230.47	11.708%	$257.4534	$257.45	$257.45	$257.50
Purchase #3	$80.65	11.811%	$90.1756	$90.18	$90.20	$90.20
Purchase #4	$131.75	8.487%	$142.9316	$142.93	$142.95	$142.90
Purchase #5	$94.52	7.358%	$101.4748	$101.47	$101.45	$101.50
Purchase #6	$161.45	12.250%	$181.2276	$181.23	$181.25	$181.20
Purchase #7	$223.47	7.418%	$240.047	$240.05	$240.05	$240.00
7 purchase totals =	$958.80		$1,053.7413	$1,053.74	$1,053.80	$1,053.70