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	$111.61	4.410%	$116.532	$116.53	$116.55	$116.50
Purchase #2	$151.43	7.701%	$163.0916	$163.09	$163.10	$163.10
Purchase #3	$137.35	3.322%	$141.9128	$141.91	$141.90	$141.90
Purchase #4	$76.88	9.372%	$84.0852	$84.09	$84.10	$84.10
Purchase #5	$146.58	3.689%	$151.9873	$151.99	$152.00	$152.00
Purchase #6	$38.83	3.362%	$40.1355	$40.14	$40.15	$40.10
Purchase #7	$103.33	8.215%	$111.8186	$111.82	$111.80	$111.80
7 purchase totals =	$766.01		$809.5630	$809.57	$809.60	$809.50