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	$122.53	9.636%	$134.337	$134.34	$134.35	$134.30
Purchase #2	$220.26	13.696%	$250.4268	$250.43	$250.45	$250.40
Purchase #3	$39.59	4.455%	$41.3537	$41.35	$41.35	$41.40
Purchase #4	$164.39	6.169%	$174.5312	$174.53	$174.55	$174.50
Purchase #5	$219.69	5.419%	$231.595	$231.60	$231.60	$231.60
Purchase #6	$249.33	8.242%	$269.8798	$269.88	$269.90	$269.90
Purchase #7	$6.73	13.330%	$7.6271	$7.63	$7.65	$7.60
7 purchase totals =	$1,022.52		$1,109.7506	$1,109.76	$1,109.85	$1,109.70