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	$66.33	8.381%	$71.8891	$71.89	$71.90	$71.90
Purchase #2	$144.30	9.758%	$158.3808	$158.38	$158.40	$158.40
Purchase #3	$166.46	9.374%	$182.064	$182.06	$182.05	$182.10
Purchase #4	$80.51	11.280%	$89.5915	$89.59	$89.60	$89.60
Purchase #5	$204.54	13.587%	$232.3308	$232.33	$232.35	$232.30
Purchase #6	$107.90	11.607%	$120.424	$120.42	$120.40	$120.40
Purchase #7	$242.45	5.725%	$256.3303	$256.33	$256.35	$256.30
7 purchase totals =	$1,012.49		$1,111.0105	$1,111.00	$1,111.05	$1,111.00