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	$196.85	9.400%	$215.3539	$215.35	$215.35	$215.40
Purchase #2	$152.25	11.177%	$169.267	$169.27	$169.25	$169.30
Purchase #3	$82.47	8.266%	$89.287	$89.29	$89.30	$89.30
Purchase #4	$238.28	6.566%	$253.9255	$253.93	$253.95	$253.90
Purchase #5	$198.94	8.487%	$215.824	$215.82	$215.80	$215.80
Purchase #6	$244.57	11.723%	$273.2409	$273.24	$273.25	$273.20
Purchase #7	$130.45	8.235%	$141.1926	$141.19	$141.20	$141.20
7 purchase totals =	$1,243.81		$1,358.0909	$1,358.09	$1,358.10	$1,358.10