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	$71.83	7.395%	$77.1418	$77.14	$77.15	$77.10
Purchase #2	$177.26	10.790%	$196.3864	$196.39	$196.40	$196.40
Purchase #3	$37.43	11.727%	$41.8194	$41.82	$41.80	$41.80
Purchase #4	$242.54	10.286%	$267.4877	$267.49	$267.50	$267.50
Purchase #5	$140.27	11.650%	$156.6115	$156.61	$156.60	$156.60
Purchase #6	$168.38	9.693%	$184.7011	$184.70	$184.70	$184.70
Purchase #7	$132.42	11.257%	$147.3265	$147.33	$147.35	$147.30
7 purchase totals =	$970.13		$1,071.4744	$1,071.48	$1,071.50	$1,071.40