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	$176.78	4.254%	$184.3002	$184.30	$184.30	$184.30
Purchase #2	$145.65	13.265%	$164.9705	$164.97	$164.95	$165.00
Purchase #3	$147.72	6.283%	$157.0012	$157.00	$157.00	$157.00
Purchase #4	$20.54	9.594%	$22.5106	$22.51	$22.50	$22.50
Purchase #5	$249.43	12.348%	$280.2296	$280.23	$280.25	$280.20
Purchase #6	$167.77	10.737%	$185.7835	$185.78	$185.80	$185.80
Purchase #7	$12.33	8.797%	$13.4147	$13.41	$13.40	$13.40
7 purchase totals =	$920.22		$1,008.2103	$1,008.20	$1,008.20	$1,008.20