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	$43.54	3.437%	$45.0365	$45.04	$45.05	$45.00
Purchase #2	$89.33	6.345%	$94.998	$95.00	$95.00	$95.00
Purchase #3	$250.41	12.201%	$280.9625	$280.96	$280.95	$281.00
Purchase #4	$76.27	9.466%	$83.4897	$83.49	$83.50	$83.50
Purchase #5	$137.28	7.477%	$147.5444	$147.54	$147.55	$147.50
Purchase #6	$59.45	7.701%	$64.0282	$64.03	$64.05	$64.00
Purchase #7	$97.93	7.724%	$105.4941	$105.49	$105.50	$105.50
7 purchase totals =	$754.21		$821.5534	$821.55	$821.60	$821.50