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	$214.97	5.750%	$227.3308	$227.33	$227.35	$227.30
Purchase #2	$78.88	10.589%	$87.2326	$87.23	$87.25	$87.20
Purchase #3	$85.82	4.815%	$89.9522	$89.95	$89.95	$90.00
Purchase #4	$111.84	12.287%	$125.5818	$125.58	$125.60	$125.60
Purchase #5	$208.50	13.775%	$237.2209	$237.22	$237.20	$237.20
Purchase #6	$174.98	8.789%	$190.359	$190.36	$190.35	$190.40
Purchase #7	$130.74	9.572%	$143.2544	$143.25	$143.25	$143.30
7 purchase totals =	$1,005.73		$1,100.9317	$1,100.92	$1,100.95	$1,101.00