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	$164.88	12.255%	$185.086	$185.09	$185.10	$185.10
Purchase #2	$61.72	7.473%	$66.3323	$66.33	$66.35	$66.30
Purchase #3	$188.88	4.377%	$197.1473	$197.15	$197.15	$197.10
Purchase #4	$67.47	6.837%	$72.0829	$72.08	$72.10	$72.10
Purchase #5	$5.70	9.622%	$6.2485	$6.25	$6.25	$6.20
Purchase #6	$220.29	4.517%	$230.2405	$230.24	$230.25	$230.20
Purchase #7	$80.77	6.367%	$85.9126	$85.91	$85.90	$85.90
7 purchase totals =	$789.71		$843.0501	$843.05	$843.10	$842.90