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	$54.81	3.306%	$56.622	$56.62	$56.60	$56.60
Purchase #2	$67.90	8.246%	$73.499	$73.50	$73.50	$73.50
Purchase #3	$52.79	4.744%	$55.2944	$55.29	$55.30	$55.30
Purchase #4	$117.51	8.739%	$127.7792	$127.78	$127.80	$127.80
Purchase #5	$231.77	7.481%	$249.1087	$249.11	$249.10	$249.10
Purchase #6	$248.77	12.656%	$280.2543	$280.25	$280.25	$280.30
Purchase #7	$40.51	9.179%	$44.2284	$44.23	$44.25	$44.20
7 purchase totals =	$814.06		$886.7860	$886.78	$886.80	$886.80