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	$103.25	9.292%	$112.844	$112.84	$112.85	$112.80
Purchase #2	$100.35	12.104%	$112.4964	$112.50	$112.50	$112.50
Purchase #3	$77.97	9.719%	$85.5479	$85.55	$85.55	$85.50
Purchase #4	$235.48	3.403%	$243.4934	$243.49	$243.50	$243.50
Purchase #5	$71.78	7.865%	$77.4255	$77.43	$77.45	$77.40
Purchase #6	$28.40	10.379%	$31.3476	$31.35	$31.35	$31.30
Purchase #7	$184.46	7.445%	$198.193	$198.19	$198.20	$198.20
7 purchase totals =	$801.69		$861.3478	$861.35	$861.40	$861.20