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	$164.90	9.454%	$180.4896	$180.49	$180.50	$180.50
Purchase #2	$216.59	6.391%	$230.4323	$230.43	$230.45	$230.40
Purchase #3	$237.87	4.802%	$249.2925	$249.29	$249.30	$249.30
Purchase #4	$55.65	10.571%	$61.5328	$61.53	$61.55	$61.50
Purchase #5	$92.69	4.592%	$96.9463	$96.95	$96.95	$96.90
Purchase #6	$55.86	4.759%	$58.5184	$58.52	$58.50	$58.50
Purchase #7	$119.71	9.254%	$130.788	$130.79	$130.80	$130.80
7 purchase totals =	$943.27		$1,007.9999	$1,008.00	$1,008.05	$1,007.90