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	$244.61	6.558%	$260.6515	$260.65	$260.65	$260.70
Purchase #2	$65.37	10.337%	$72.1273	$72.13	$72.15	$72.10
Purchase #3	$141.78	6.308%	$150.7235	$150.72	$150.70	$150.70
Purchase #4	$58.92	4.227%	$61.4105	$61.41	$61.40	$61.40
Purchase #5	$80.80	7.175%	$86.5974	$86.60	$86.60	$86.60
Purchase #6	$231.33	12.723%	$260.7621	$260.76	$260.75	$260.80
Purchase #7	$220.88	8.783%	$240.2799	$240.28	$240.30	$240.30
7 purchase totals =	$1,043.69		$1,132.5522	$1,132.55	$1,132.55	$1,132.60