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	$185.81	12.579%	$209.183	$209.18	$209.20	$209.20
Purchase #2	$221.57	5.157%	$232.9964	$233.00	$233.00	$233.00
Purchase #3	$169.78	9.301%	$185.5712	$185.57	$185.55	$185.60
Purchase #4	$131.38	8.155%	$142.094	$142.09	$142.10	$142.10
Purchase #5	$132.56	6.746%	$141.5025	$141.50	$141.50	$141.50
Purchase #6	$80.27	3.670%	$83.2159	$83.22	$83.20	$83.20
Purchase #7	$79.60	9.712%	$87.3308	$87.33	$87.35	$87.30
7 purchase totals =	$1,000.97		$1,081.8938	$1,081.89	$1,081.90	$1,081.90