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	$182.45	11.750%	$203.8879	$203.89	$203.90	$203.90
Purchase #2	$100.85	3.228%	$104.1054	$104.11	$104.10	$104.10
Purchase #3	$76.84	4.769%	$80.5045	$80.50	$80.50	$80.50
Purchase #4	$31.45	3.440%	$32.5319	$32.53	$32.55	$32.50
Purchase #5	$149.68	11.799%	$167.3407	$167.34	$167.35	$167.30
Purchase #6	$28.86	12.596%	$32.4952	$32.50	$32.50	$32.50
Purchase #7	$130.40	6.327%	$138.6504	$138.65	$138.65	$138.70
7 purchase totals =	$700.53		$759.5160	$759.52	$759.55	$759.50