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	$168.28	3.500%	$174.1698	$174.17	$174.15	$174.20
Purchase #2	$225.84	10.461%	$249.4651	$249.47	$249.45	$249.50
Purchase #3	$177.44	11.482%	$197.8137	$197.81	$197.80	$197.80
Purchase #4	$56.83	8.853%	$61.8612	$61.86	$61.85	$61.90
Purchase #5	$173.55	13.458%	$196.9064	$196.91	$196.90	$196.90
Purchase #6	$237.71	9.586%	$260.4969	$260.50	$260.50	$260.50
Purchase #7	$88.85	4.475%	$92.826	$92.83	$92.85	$92.80
7 purchase totals =	$1,128.50		$1,233.5391	$1,233.55	$1,233.50	$1,233.60