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	$162.43	9.732%	$178.2377	$178.24	$178.25	$178.20
Purchase #2	$222.48	12.640%	$250.6015	$250.60	$250.60	$250.60
Purchase #3	$15.96	6.268%	$16.9604	$16.96	$16.95	$17.00
Purchase #4	$72.70	7.401%	$78.0805	$78.08	$78.10	$78.10
Purchase #5	$64.67	10.484%	$71.45	$71.45	$71.45	$71.50
Purchase #6	$193.89	10.600%	$214.4423	$214.44	$214.45	$214.40
Purchase #7	$182.25	3.767%	$189.1154	$189.12	$189.10	$189.10
7 purchase totals =	$914.38		$998.8878	$998.89	$998.90	$998.90