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	$112.76	4.525%	$117.8624	$117.86	$117.85	$117.90
Purchase #2	$86.99	4.241%	$90.6792	$90.68	$90.70	$90.70
Purchase #3	$162.51	13.527%	$184.4927	$184.49	$184.50	$184.50
Purchase #4	$212.62	7.168%	$227.8606	$227.86	$227.85	$227.90
Purchase #5	$152.56	7.843%	$164.5253	$164.53	$164.55	$164.50
Purchase #6	$127.87	8.224%	$138.386	$138.39	$138.40	$138.40
Purchase #7	$67.41	7.712%	$72.6087	$72.61	$72.60	$72.60
7 purchase totals =	$922.72		$996.4149	$996.42	$996.45	$996.50