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	$100.56	5.857%	$106.4498	$106.45	$106.45	$106.40
Purchase #2	$137.30	13.725%	$156.1444	$156.14	$156.15	$156.10
Purchase #3	$229.67	11.693%	$256.5253	$256.53	$256.55	$256.50
Purchase #4	$56.28	3.654%	$58.3365	$58.34	$58.35	$58.30
Purchase #5	$101.50	9.704%	$111.3496	$111.35	$111.35	$111.30
Purchase #6	$94.53	6.242%	$100.4306	$100.43	$100.45	$100.40
Purchase #7	$211.64	3.360%	$218.7511	$218.75	$218.75	$218.80
7 purchase totals =	$931.48		$1,007.9873	$1,007.99	$1,008.05	$1,007.80