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	$249.55	4.268%	$260.2008	$260.20	$260.20	$260.20
Purchase #2	$18.92	5.457%	$19.9525	$19.95	$19.95	$20.00
Purchase #3	$125.31	13.401%	$142.1028	$142.10	$142.10	$142.10
Purchase #4	$180.81	4.620%	$189.1634	$189.16	$189.15	$189.20
Purchase #5	$122.64	13.711%	$139.4552	$139.46	$139.45	$139.50
Purchase #6	$56.79	4.738%	$59.4807	$59.48	$59.50	$59.50
Purchase #7	$215.49	10.738%	$238.6293	$238.63	$238.65	$238.60
7 purchase totals =	$969.51		$1,048.9847	$1,048.98	$1,049.00	$1,049.10