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	$154.96	3.408%	$160.241	$160.24	$160.25	$160.20
Purchase #2	$246.43	13.826%	$280.5014	$280.50	$280.50	$280.50
Purchase #3	$174.54	6.329%	$185.5866	$185.59	$185.60	$185.60
Purchase #4	$19.96	4.765%	$20.9111	$20.91	$20.90	$20.90
Purchase #5	$29.80	5.554%	$31.4551	$31.46	$31.45	$31.50
Purchase #6	$144.32	4.296%	$150.52	$150.52	$150.50	$150.50
Purchase #7	$231.73	13.349%	$262.6636	$262.66	$262.65	$262.70
7 purchase totals =	$1,001.74		$1,091.8788	$1,091.88	$1,091.85	$1,091.90