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	$214.44	8.791%	$233.2914	$233.29	$233.30	$233.30
Purchase #2	$217.50	7.232%	$233.2296	$233.23	$233.25	$233.20
Purchase #3	$218.45	10.294%	$240.9372	$240.94	$240.95	$240.90
Purchase #4	$250.84	11.711%	$280.2159	$280.22	$280.20	$280.20
Purchase #5	$10.42	4.167%	$10.8542	$10.85	$10.85	$10.90
Purchase #6	$21.43	4.645%	$22.4254	$22.43	$22.45	$22.40
Purchase #7	$162.33	3.516%	$168.0375	$168.04	$168.05	$168.00
7 purchase totals =	$1,095.41		$1,188.9912	$1,189.00	$1,189.05	$1,188.90