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	$219.53	9.314%	$239.977	$239.98	$240.00	$240.00
Purchase #2	$66.96	9.665%	$73.4317	$73.43	$73.45	$73.40
Purchase #3	$122.39	7.384%	$131.4273	$131.43	$131.45	$131.40
Purchase #4	$44.93	4.616%	$47.004	$47.00	$47.00	$47.00
Purchase #5	$199.71	5.221%	$210.1369	$210.14	$210.15	$210.10
Purchase #6	$180.51	5.529%	$190.4904	$190.49	$190.50	$190.50
Purchase #7	$180.91	5.371%	$190.6267	$190.63	$190.65	$190.60
7 purchase totals =	$1,014.94		$1,083.0940	$1,083.10	$1,083.20	$1,083.00