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	$120.33	5.376%	$126.7989	$126.80	$126.80	$126.80
Purchase #2	$207.42	6.732%	$221.3835	$221.38	$221.40	$221.40
Purchase #3	$92.81	13.840%	$105.6549	$105.65	$105.65	$105.70
Purchase #4	$186.85	5.683%	$197.4687	$197.47	$197.45	$197.50
Purchase #5	$168.80	11.290%	$187.8575	$187.86	$187.85	$187.90
Purchase #6	$115.64	13.792%	$131.5891	$131.59	$131.60	$131.60
Purchase #7	$82.72	9.184%	$90.317	$90.32	$90.30	$90.30
7 purchase totals =	$974.57		$1,061.0696	$1,061.07	$1,061.05	$1,061.20