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	$237.42	10.457%	$262.247	$262.25	$262.25	$262.20
Purchase #2	$112.96	4.751%	$118.3267	$118.33	$118.35	$118.30
Purchase #3	$131.90	9.405%	$144.3052	$144.31	$144.30	$144.30
Purchase #4	$73.59	6.373%	$78.2799	$78.28	$78.30	$78.30
Purchase #5	$35.76	6.520%	$38.0916	$38.09	$38.10	$38.10
Purchase #6	$25.45	13.395%	$28.859	$28.86	$28.85	$28.90
Purchase #7	$169.34	5.537%	$178.7164	$178.72	$178.70	$178.70
7 purchase totals =	$786.42		$848.8258	$848.84	$848.85	$848.80