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	$188.31	13.552%	$213.8298	$213.83	$213.85	$213.80
Purchase #2	$189.47	4.156%	$197.3444	$197.34	$197.35	$197.30
Purchase #3	$6.89	3.523%	$7.1327	$7.13	$7.15	$7.10
Purchase #4	$154.86	8.334%	$167.766	$167.77	$167.75	$167.80
Purchase #5	$185.80	7.593%	$199.9078	$199.91	$199.90	$199.90
Purchase #6	$177.90	10.690%	$196.9175	$196.92	$196.90	$196.90
Purchase #7	$137.99	4.861%	$144.6977	$144.70	$144.70	$144.70
7 purchase totals =	$1,041.22		$1,127.5959	$1,127.60	$1,127.60	$1,127.50