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	$158.32	12.648%	$178.3443	$178.34	$178.35	$178.30
Purchase #2	$248.45	12.818%	$280.2963	$280.30	$280.30	$280.30
Purchase #3	$105.92	10.163%	$116.6846	$116.68	$116.70	$116.70
Purchase #4	$89.50	10.860%	$99.2197	$99.22	$99.20	$99.20
Purchase #5	$16.45	11.202%	$18.2927	$18.29	$18.30	$18.30
Purchase #6	$83.78	4.776%	$87.7813	$87.78	$87.80	$87.80
Purchase #7	$223.44	5.409%	$235.5259	$235.53	$235.55	$235.50
7 purchase totals =	$925.86		$1,016.1448	$1,016.14	$1,016.20	$1,016.10