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	$67.86	13.616%	$77.0998	$77.10	$77.10	$77.10
Purchase #2	$56.31	12.405%	$63.2953	$63.30	$63.30	$63.30
Purchase #3	$38.55	12.706%	$43.4482	$43.45	$43.45	$43.40
Purchase #4	$80.69	13.843%	$91.8599	$91.86	$91.85	$91.90
Purchase #5	$99.77	8.732%	$108.4819	$108.48	$108.50	$108.50
Purchase #6	$159.51	12.277%	$179.093	$179.09	$179.10	$179.10
Purchase #7	$146.57	10.723%	$162.2867	$162.29	$162.30	$162.30
7 purchase totals =	$649.26		$725.5648	$725.57	$725.60	$725.60