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	$148.30	5.295%	$156.1525	$156.15	$156.15	$156.20
Purchase #2	$79.27	7.154%	$84.941	$84.94	$84.95	$84.90
Purchase #3	$62.30	6.151%	$66.1321	$66.13	$66.15	$66.10
Purchase #4	$28.81	10.214%	$31.7527	$31.75	$31.75	$31.80
Purchase #5	$78.65	3.595%	$81.4775	$81.48	$81.50	$81.50
Purchase #6	$222.53	4.477%	$232.4927	$232.49	$232.50	$232.50
Purchase #7	$117.86	5.119%	$123.8933	$123.89	$123.90	$123.90
7 purchase totals =	$737.72		$776.8418	$776.83	$776.90	$776.90