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	$111.82	3.357%	$115.5738	$115.57	$115.55	$115.60
Purchase #2	$195.53	12.381%	$219.7386	$219.74	$219.75	$219.70
Purchase #3	$81.52	9.857%	$89.5554	$89.56	$89.55	$89.60
Purchase #4	$199.56	8.413%	$216.349	$216.35	$216.35	$216.30
Purchase #5	$184.79	7.730%	$199.0743	$199.07	$199.05	$199.10
Purchase #6	$141.42	13.161%	$160.0323	$160.03	$160.05	$160.00
Purchase #7	$115.48	13.761%	$131.3712	$131.37	$131.35	$131.40
7 purchase totals =	$1,030.12		$1,131.6946	$1,131.69	$1,131.65	$1,131.70