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	$239.96	11.277%	$267.0203	$267.02	$267.00	$267.00
Purchase #2	$101.38	10.519%	$112.0442	$112.04	$112.05	$112.00
Purchase #3	$54.47	10.238%	$60.0466	$60.05	$60.05	$60.00
Purchase #4	$32.86	12.725%	$37.0414	$37.04	$37.05	$37.00
Purchase #5	$143.71	5.711%	$151.9173	$151.92	$151.90	$151.90
Purchase #6	$212.98	7.481%	$228.913	$228.91	$228.90	$228.90
Purchase #7	$117.32	9.393%	$128.3399	$128.34	$128.35	$128.30
7 purchase totals =	$902.68		$985.3227	$985.32	$985.30	$985.10