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	$29.57	10.328%	$32.624	$32.62	$32.60	$32.60
Purchase #2	$111.52	11.810%	$124.6905	$124.69	$124.70	$124.70
Purchase #3	$91.65	9.702%	$100.5419	$100.54	$100.55	$100.50
Purchase #4	$121.32	9.744%	$133.1414	$133.14	$133.15	$133.10
Purchase #5	$188.60	10.574%	$208.5426	$208.54	$208.55	$208.50
Purchase #6	$154.89	4.627%	$162.0568	$162.06	$162.05	$162.10
Purchase #7	$243.29	6.296%	$258.6075	$258.61	$258.60	$258.60
7 purchase totals =	$940.84		$1,020.2047	$1,020.20	$1,020.20	$1,020.10