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	$118.54	13.817%	$134.9187	$134.92	$134.90	$134.90
Purchase #2	$129.67	11.215%	$144.2125	$144.21	$144.20	$144.20
Purchase #3	$182.30	9.856%	$200.2675	$200.27	$200.25	$200.30
Purchase #4	$52.46	6.599%	$55.9218	$55.92	$55.90	$55.90
Purchase #5	$149.38	6.632%	$159.2869	$159.29	$159.30	$159.30
Purchase #6	$156.94	10.484%	$173.3936	$173.39	$173.40	$173.40
Purchase #7	$189.92	5.774%	$200.886	$200.89	$200.90	$200.90
7 purchase totals =	$979.21		$1,068.8870	$1,068.89	$1,068.85	$1,068.90