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	$75.94	8.804%	$82.6258	$82.63	$82.65	$82.60
Purchase #2	$249.30	10.775%	$276.1621	$276.16	$276.15	$276.20
Purchase #3	$198.32	7.562%	$213.317	$213.32	$213.30	$213.30
Purchase #4	$214.59	6.781%	$229.1413	$229.14	$229.15	$229.10
Purchase #5	$196.82	4.457%	$205.5923	$205.59	$205.60	$205.60
Purchase #6	$219.77	4.720%	$230.1431	$230.14	$230.15	$230.10
Purchase #7	$45.33	10.475%	$50.0783	$50.08	$50.10	$50.10
7 purchase totals =	$1,200.07		$1,287.0599	$1,287.06	$1,287.10	$1,287.00