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	$241.80	9.548%	$264.8871	$264.89	$264.90	$264.90
Purchase #2	$72.27	13.681%	$82.1573	$82.16	$82.15	$82.20
Purchase #3	$81.35	13.526%	$92.3534	$92.35	$92.35	$92.40
Purchase #4	$65.72	9.329%	$71.851	$71.85	$71.85	$71.90
Purchase #5	$60.45	12.229%	$67.8424	$67.84	$67.85	$67.80
Purchase #6	$50.84	8.273%	$55.046	$55.05	$55.05	$55.00
Purchase #7	$61.42	4.296%	$64.0586	$64.06	$64.05	$64.10
7 purchase totals =	$633.85		$698.1958	$698.20	$698.20	$698.30