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	$23.74	9.187%	$25.921	$25.92	$25.90	$25.90
Purchase #2	$13.77	6.709%	$14.6938	$14.69	$14.70	$14.70
Purchase #3	$187.64	12.282%	$210.6859	$210.69	$210.70	$210.70
Purchase #4	$54.26	9.292%	$59.3018	$59.30	$59.30	$59.30
Purchase #5	$233.67	4.376%	$243.8954	$243.90	$243.90	$243.90
Purchase #6	$221.42	11.325%	$246.4958	$246.50	$246.50	$246.50
Purchase #7	$76.39	8.532%	$82.9076	$82.91	$82.90	$82.90
7 purchase totals =	$810.89		$883.9013	$883.91	$883.90	$883.90