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	$34.39	9.182%	$37.5477	$37.55	$37.55	$37.50
Purchase #2	$141.32	6.657%	$150.7277	$150.73	$150.75	$150.70
Purchase #3	$187.70	6.300%	$199.5251	$199.53	$199.55	$199.50
Purchase #4	$228.57	5.258%	$240.5882	$240.59	$240.60	$240.60
Purchase #5	$75.52	9.606%	$82.7745	$82.77	$82.75	$82.80
Purchase #6	$213.69	6.563%	$227.7145	$227.71	$227.70	$227.70
Purchase #7	$83.62	11.539%	$93.2689	$93.27	$93.25	$93.30
7 purchase totals =	$964.81		$1,032.1466	$1,032.15	$1,032.15	$1,032.10