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	$233.39	5.650%	$246.5765	$246.58	$246.60	$246.60
Purchase #2	$43.56	3.676%	$45.1613	$45.16	$45.15	$45.20
Purchase #3	$73.63	7.134%	$78.8828	$78.88	$78.90	$78.90
Purchase #4	$231.76	7.587%	$249.3436	$249.34	$249.35	$249.30
Purchase #5	$45.77	13.644%	$52.0149	$52.01	$52.00	$52.00
Purchase #6	$226.41	3.136%	$233.5102	$233.51	$233.50	$233.50
Purchase #7	$84.40	12.232%	$94.7238	$94.72	$94.70	$94.70
7 purchase totals =	$938.92		$1,000.2131	$1,000.20	$1,000.20	$1,000.20