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	$233.27	5.150%	$245.2834	$245.28	$245.30	$245.30
Purchase #2	$114.79	7.588%	$123.5003	$123.50	$123.50	$123.50
Purchase #3	$129.66	9.683%	$142.215	$142.22	$142.20	$142.20
Purchase #4	$119.83	9.167%	$130.8148	$130.81	$130.80	$130.80
Purchase #5	$214.62	12.246%	$240.9024	$240.90	$240.90	$240.90
Purchase #6	$72.97	7.352%	$78.3348	$78.33	$78.35	$78.30
Purchase #7	$111.61	7.145%	$119.5845	$119.58	$119.60	$119.60
7 purchase totals =	$996.75		$1,080.6352	$1,080.62	$1,080.65	$1,080.60