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	$111.37	3.534%	$115.3058	$115.31	$115.30	$115.30
Purchase #2	$150.38	11.753%	$168.0542	$168.05	$168.05	$168.10
Purchase #3	$190.47	5.278%	$200.523	$200.52	$200.50	$200.50
Purchase #4	$43.88	7.398%	$47.1262	$47.13	$47.15	$47.10
Purchase #5	$242.41	11.526%	$270.3502	$270.35	$270.35	$270.40
Purchase #6	$181.29	10.440%	$200.2167	$200.22	$200.20	$200.20
Purchase #7	$90.27	6.229%	$95.8929	$95.89	$95.90	$95.90
7 purchase totals =	$1,010.07		$1,097.4690	$1,097.47	$1,097.45	$1,097.50