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	$196.76	13.365%	$223.057	$223.06	$223.05	$223.10
Purchase #2	$151.71	10.474%	$167.6001	$167.60	$167.60	$167.60
Purchase #3	$59.35	11.866%	$66.3925	$66.39	$66.40	$66.40
Purchase #4	$37.66	9.745%	$41.33	$41.33	$41.35	$41.30
Purchase #5	$238.57	12.761%	$269.0139	$269.01	$269.00	$269.00
Purchase #6	$63.55	9.644%	$69.6788	$69.68	$69.70	$69.70
Purchase #7	$232.81	10.179%	$256.5077	$256.51	$256.50	$256.50
7 purchase totals =	$980.41		$1,093.5800	$1,093.58	$1,093.60	$1,093.60