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	$105.25	13.147%	$119.0872	$119.09	$119.10	$119.10
Purchase #2	$97.78	4.793%	$102.4666	$102.47	$102.45	$102.50
Purchase #3	$108.25	7.364%	$116.2215	$116.22	$116.20	$116.20
Purchase #4	$140.93	3.859%	$146.3685	$146.37	$146.35	$146.40
Purchase #5	$84.25	5.682%	$89.0371	$89.04	$89.05	$89.00
Purchase #6	$140.79	13.721%	$160.1078	$160.11	$160.10	$160.10
Purchase #7	$160.30	7.216%	$171.8672	$171.87	$171.85	$171.90
7 purchase totals =	$837.55		$905.1559	$905.17	$905.10	$905.20