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	$246.94	8.328%	$267.5052	$267.51	$267.50	$267.50
Purchase #2	$134.81	3.224%	$139.1563	$139.16	$139.15	$139.20
Purchase #3	$103.53	12.329%	$116.2942	$116.29	$116.30	$116.30
Purchase #4	$176.98	9.226%	$193.3082	$193.31	$193.30	$193.30
Purchase #5	$151.59	7.411%	$162.8243	$162.82	$162.80	$162.80
Purchase #6	$131.57	11.793%	$147.0861	$147.09	$147.10	$147.10
Purchase #7	$63.56	6.133%	$67.4581	$67.46	$67.45	$67.50
7 purchase totals =	$1,008.98		$1,093.6324	$1,093.64	$1,093.60	$1,093.70