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	$207.53	4.370%	$216.5991	$216.60	$216.60	$216.60
Purchase #2	$71.93	9.212%	$78.5562	$78.56	$78.55	$78.60
Purchase #3	$194.71	5.295%	$205.0199	$205.02	$205.00	$205.00
Purchase #4	$144.74	4.244%	$150.8828	$150.88	$150.90	$150.90
Purchase #5	$38.35	11.659%	$42.8212	$42.82	$42.80	$42.80
Purchase #6	$182.52	8.488%	$198.0123	$198.01	$198.00	$198.00
Purchase #7	$133.66	13.174%	$151.2684	$151.27	$151.25	$151.30
7 purchase totals =	$973.44		$1,043.1599	$1,043.16	$1,043.10	$1,043.20