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	$108.81	6.392%	$115.7651	$115.77	$115.75	$115.80
Purchase #2	$31.29	3.742%	$32.4609	$32.46	$32.45	$32.50
Purchase #3	$213.98	3.492%	$221.4522	$221.45	$221.45	$221.50
Purchase #4	$234.55	9.520%	$256.8792	$256.88	$256.90	$256.90
Purchase #5	$218.69	4.187%	$227.8466	$227.85	$227.85	$227.80
Purchase #6	$45.35	11.206%	$50.4319	$50.43	$50.45	$50.40
Purchase #7	$148.77	5.630%	$157.1458	$157.15	$157.15	$157.10
7 purchase totals =	$1,001.44		$1,061.9817	$1,061.99	$1,062.00	$1,062.00