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	$168.25	8.704%	$182.8945	$182.89	$182.90	$182.90
Purchase #2	$198.98	12.617%	$224.0853	$224.09	$224.10	$224.10
Purchase #3	$12.26	6.684%	$13.0795	$13.08	$13.10	$13.10
Purchase #4	$24.70	13.179%	$27.9552	$27.96	$27.95	$28.00
Purchase #5	$172.93	10.778%	$191.5684	$191.57	$191.55	$191.60
Purchase #6	$73.47	7.393%	$78.9016	$78.90	$78.90	$78.90
Purchase #7	$193.58	8.301%	$209.6491	$209.65	$209.65	$209.60
7 purchase totals =	$844.17		$928.1336	$928.14	$928.15	$928.20