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	$84.60	12.361%	$95.0574	$95.06	$95.05	$95.10
Purchase #2	$180.85	6.841%	$193.2219	$193.22	$193.20	$193.20
Purchase #3	$206.57	4.396%	$215.6508	$215.65	$215.65	$215.70
Purchase #4	$127.56	9.648%	$139.867	$139.87	$139.85	$139.90
Purchase #5	$63.41	13.387%	$71.8987	$71.90	$71.90	$71.90
Purchase #6	$175.80	3.682%	$182.273	$182.27	$182.25	$182.30
Purchase #7	$168.27	12.223%	$188.8376	$188.84	$188.85	$188.80
7 purchase totals =	$1,007.06		$1,086.8064	$1,086.81	$1,086.75	$1,086.90