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	$43.64	10.132%	$48.0616	$48.06	$48.05	$48.10
Purchase #2	$113.96	4.697%	$119.3127	$119.31	$119.30	$119.30
Purchase #3	$81.88	10.846%	$90.7607	$90.76	$90.75	$90.80
Purchase #4	$58.52	4.767%	$61.3096	$61.31	$61.30	$61.30
Purchase #5	$179.92	9.752%	$197.4658	$197.47	$197.45	$197.50
Purchase #6	$132.36	12.218%	$148.5317	$148.53	$148.55	$148.50
Purchase #7	$83.60	4.859%	$87.6621	$87.66	$87.65	$87.70
7 purchase totals =	$693.88		$753.1042	$753.10	$753.05	$753.20