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	$163.54	5.242%	$172.1128	$172.11	$172.10	$172.10
Purchase #2	$134.81	13.389%	$152.8597	$152.86	$152.85	$152.90
Purchase #3	$137.49	9.329%	$150.3164	$150.32	$150.30	$150.30
Purchase #4	$215.38	3.271%	$222.4251	$222.43	$222.45	$222.40
Purchase #5	$136.96	7.545%	$147.2936	$147.29	$147.30	$147.30
Purchase #6	$96.88	8.518%	$105.1322	$105.13	$105.15	$105.10
Purchase #7	$10.75	8.337%	$11.6462	$11.65	$11.65	$11.60
7 purchase totals =	$895.81		$961.7860	$961.79	$961.80	$961.70