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	$106.76	5.457%	$112.5859	$112.59	$112.60	$112.60
Purchase #2	$132.63	3.747%	$137.5996	$137.60	$137.60	$137.60
Purchase #3	$96.60	13.354%	$109.5	$109.50	$109.50	$109.50
Purchase #4	$39.66	10.541%	$43.8406	$43.84	$43.85	$43.80
Purchase #5	$219.75	5.243%	$231.2715	$231.27	$231.25	$231.30
Purchase #6	$31.77	5.617%	$33.5545	$33.55	$33.55	$33.60
Purchase #7	$23.53	12.817%	$26.5458	$26.55	$26.55	$26.50
7 purchase totals =	$650.70		$694.8979	$694.90	$694.90	$694.90