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	$39.82	6.377%	$42.3593	$42.36	$42.35	$42.40
Purchase #2	$153.47	5.618%	$162.0919	$162.09	$162.10	$162.10
Purchase #3	$233.27	6.590%	$248.6425	$248.64	$248.65	$248.60
Purchase #4	$123.42	3.191%	$127.3583	$127.36	$127.35	$127.40
Purchase #5	$240.80	12.380%	$270.611	$270.61	$270.60	$270.60
Purchase #6	$169.51	6.268%	$180.1349	$180.13	$180.15	$180.10
Purchase #7	$19.70	13.853%	$22.429	$22.43	$22.45	$22.40
7 purchase totals =	$979.99		$1,053.6269	$1,053.62	$1,053.65	$1,053.60