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	$133.83	7.249%	$143.5313	$143.53	$143.55	$143.50
Purchase #2	$59.34	9.602%	$65.0378	$65.04	$65.05	$65.00
Purchase #3	$40.25	6.128%	$42.7165	$42.72	$42.70	$42.70
Purchase #4	$141.34	9.228%	$154.3829	$154.38	$154.40	$154.40
Purchase #5	$202.70	3.675%	$210.1492	$210.15	$210.15	$210.10
Purchase #6	$242.76	11.162%	$269.8569	$269.86	$269.85	$269.90
Purchase #7	$192.48	7.831%	$207.5531	$207.55	$207.55	$207.60
7 purchase totals =	$1,012.70		$1,093.2277	$1,093.23	$1,093.25	$1,093.20