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	$130.93	10.801%	$145.0717	$145.07	$145.05	$145.10
Purchase #2	$213.53	5.197%	$224.6272	$224.63	$224.65	$224.60
Purchase #3	$194.43	10.785%	$215.3993	$215.40	$215.40	$215.40
Purchase #4	$59.52	3.211%	$61.4312	$61.43	$61.45	$61.40
Purchase #5	$104.76	6.428%	$111.494	$111.49	$111.50	$111.50
Purchase #6	$103.90	13.211%	$117.6262	$117.63	$117.65	$117.60
Purchase #7	$78.88	4.108%	$82.1204	$82.12	$82.10	$82.10
7 purchase totals =	$885.95		$957.7700	$957.77	$957.80	$957.70