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	$239.49	10.440%	$264.4928	$264.49	$264.50	$264.50
Purchase #2	$103.93	12.115%	$116.5211	$116.52	$116.50	$116.50
Purchase #3	$44.85	3.763%	$46.5377	$46.54	$46.55	$46.50
Purchase #4	$189.35	11.663%	$211.4339	$211.43	$211.45	$211.40
Purchase #5	$184.96	8.170%	$200.0712	$200.07	$200.05	$200.10
Purchase #6	$105.38	12.112%	$118.1436	$118.14	$118.15	$118.10
Purchase #7	$92.46	8.483%	$100.3034	$100.30	$100.30	$100.30
7 purchase totals =	$960.42		$1,057.5037	$1,057.49	$1,057.50	$1,057.40